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SiiTENORMAL  SCHOOL 


of  CALIFORNi* 

LOS  ANGELES 
UBKARY 


BOTANY  ALL  THE  YEAR 
ROUND 

A  PRACTICAL   TEXT-BOOK  FOR  SCHOOLS 


BY 


E.    F.    ANDREWS 

HIGH    SCHOOL,   WASHINGTON,   GEORGIA 

COMPLIMENTS 

AMERICAN  BOOK  CO. 


A.  F.  GUNN,  Gton'l 
PINE  &  BATTERY 

SAN    FRANCISCO. 


NEW  YORK  •:•  CINCINNATI  •:•  CHICAGO 

AMERICAN    BOOK    COMPANY 


COPYRIGHT.  1903,  BY 
E.    F.   ANDREWS. 


ENTERED  AT  STATIONERS'  HALL,  LONDON. 


tNDREWS  S   BOTANY. 

w.  P.  4 


(V  n 
A  i> 


PREFACE 

MOST  of  the  recent  text-books  of  botany,  excellent 
as  many  of  them  are,  fail  to  meet  the  conditions  of  the 
average  public  school,  where  expensive  laboratory  appli- 
ances are  out  of  the  question,  and  time  to  make  a  proper 
use  of  them  is  equally  unattainable.  It  is  one  of  the 
anomalies  of  our  educational  system  that  the  study  of 
plants,  if  provided  for  at  all,  should  be  confined  mainly  to 
city  schools,  where  it  is  necessarily  carried  on  under  disad- 
vantageous conditions,  while  it  is  almost  entirely  neglected 
in  the  country,  where  the  great  laboratory  of  nature  stands 
invitingly  open  at  every  schoolhouse  door. 

The  writer  believes  that  this  neglect  is  largely  due  to  the 
want  of  a  text-book  suited  to  general  use,  in  which  the 
subject  is  treated  in  a  manner  at  once  simple,  practical,  and 
scientific.  It  is  with  a  desire  to  meet  this  need  and  to 
encourage  a  more  general  adoption  of  botanical  studies  in 
the  public  schools  that  the  present  work  has  been  under- 
taken. It  aims,  in  the  first  place,  to  lead  the  pupil  to  nature 
for  the  objects  of  each  lesson  ;  and  in  the  second  place, 
to  provide  that  the  proper  material  shall  be  always  avail- 
able by  so  arranging  the  lessons  that  each  subject  will  be 
taken  up  at  just  the  time  of  the  year  when  the  material  for 
it  is  most  abundant.  In  this  way  the  study  can  be  carried 
on  all  the  year  round,  a  plan  which  will  be  found  much 
better  than  crowding  the  whole  course  into  a  few  weeks 
of  the  spring  term. 

In  order  to  provide  for  this  all  the  year  round  course  it 

has  been  necessary  to  depart  somewhat  from  the  usual  order 

of  arrangement,  but  years  of  experience  have  convinced  the 

writer  that  the  advantages  to  be  gained  by  having  fresh 

3 


4  PREFACE 

material  always  at  hand  are  sufficient  to  outweigh  other 
considerations  that  might  be  advanced  in  favor  of  estab- 
lished methods.  The  leaf  has  been  selected  as  the  starting 
point  mainly  because  it  is  the  most  convenient  material  at 
hand  in  September,  when  the  schools  begin;  and  it  is 
such  an  important  and  fundamental  part  of  the  plant  that 
a  thorough  acquaintance  with  its  nature  and  functions  will 
clear  the  way  to  an  understanding  of  many  of  the  problems 
that  will  face  the  student  later. 

It  is  not  expected  that  all  the  work  outlined  in  the 
book  will  be  done  just  as  it  is  written,  and  much  of  it  may 
even  have  to  be  omitted  altogether.  Each  teacher  can 
select  such  parts  as  are  suited  to  the  circumstances  of  his 
school,  passing  lightly  over  some  topics,  giving  more 
attention  to  others,  as  material  and  opportunity  may 
suggest.  The  study  of  botany  is  necessarily  sectional 
to  some  extent,  because  nature  is  so,  but  the  method 
here  outlined  is  of  universal  application  and  every  teacher 
can  select  his  own  specimens  in  accordance  with  the 
directions  given  in  the  body  of  the  book.  Prominence  is 
given  to  the  more  familiar  forms  of  vegetation  presented 
by  the  seed-bearing  plants,  as  the  author  believes  that  for 
ordinary  purposes  the  best  results  are  to  be  obtained  by 
proceeding  from  the  familiar  and  well  known  to  the  more 
primitive  and  obscure  forms.  The  reverse  order  may  be 
better  for  the  trained  investigator;  the  other  is  simpler 
and  more  attractive,  and  for  ordinary  purposes  the  only 
practicable  one.  The  average  boy  and  girl  will  learn  more 
of  what  it  concerns  them  to  know  about  stem  structure,  for 
instance,  from  a  cornstalk,  and  a  handful  of  chips,  or  even 
from  the  graining  of  the  timber  out  of  which  their  desks 
are  made,  than  from  the  most  elaborate  study  of  the  xylem 
and  the  phloem  and  the  collenchymatous  tissues.  For  we 
must  bear  in  mind  that  the  object  of  teaching  botany  in 
the  common  schools  is  not  to  train  experts  and  investigators 
but  intelligent  observers. 

In  giving  the  botanical  names  of  plants  the  terminology 
of  Gray's  handbooks  is  adhered  to,  partly  because,  they 


PREFACE  5 

are  at  present  the  most  generally  available  for  school  use, 
and  more  especially  because  the  new  terminology  is  in 
such  an  unsettled  state  that  nobody  can  say  what  it  will 
be  to-morrow  or  next  day.  Hence,  while  recognizing  the 
desirability  of  some  of  the  changes  proposed,  the  author 
does  not  think  it  advisable  to  confuse  the  beginner  by 
introducing  him  to  a  system  that  is  undergoing  a  period 
of  transition.  After  all,  this  is  a  mere  matter  of  names, 
and  does  not  affect  the  point  that  ought  to  be  kept  in  view 
—  the  hereditary  relationships  of  plants. 

The  experiments  described  are  for  the  most  part  very 
simple,  requiring  no  appliances  but  such  as  the  ingenuity 
of  the  teacher  and  pupils  can  easily  devise,  as  will  be 
seen  by  a  glance  at  the  list  on  pages  12  and  13  of  the  text. 

Teachers  trained  in  normal  schools,  where  all  the 
material  needed  for  their  work  is  furnished  by  the  State, 
and  ample  time  allowed  them,  are  often  completely  at  a 
loss  when  transferred  to  country  schools,  where  no  provi- 
sion is  made  for  laboratory  work,  and  the  patrons  grumble 
if  called  upon  to  buy  so  much  as  a  drawing  book  or  a  hand 
lens.  Too  often  they  can  think  of  no  other  resource  than 
to  drop  botany  from  the  curriculum  altogether  rather  than 
depart  from  what  they  have  been  taught  to  consider  the 
only  scientific  method.  It  is  hoped  that  the  present  volume 
may  suggest  a  better  way  out  of  the  difficulty,  and  also 
that  it  may  be  a  help  to  those  who  have  not  enjoyed  the 
advantage  of  a  technical  training. 

The  writer  would  not  underrate  the  value  of  histological 
studies  or  the  advantages  of  a  well  equipped  laboratory, 
but  since  these  are  at  present  clearly  out  of  the  reach  of 
the  great  majority  of  the  school  population,  and  more 
especially  of  that  very  class  to  whom  the  study  of  plants 
is  of  the  greatest  practical  importance  and  into  whose 
lives  it  would  bring  the  greatest  amount  of  pleasure  and 
of  intellectual  enlargement,  it  has  been  made  the  aim  of 
this  book  to  show  that  botany  can  be  taught  to  some  pur- 
pose by  means  within  the  reach  of  everybody.  It  has 
also  been  the  author's  aim  to  keep  constantly  in  view  the 


6  PREFACE 

intimate  relations  between  botany  and  agriculture.  The 
practical  questions  at  the  end  of  each  section,  it  is  hoped, 
will  have  the  effect  of  bringing  out  these  relations  more 
clearly  and  at  the  same  time  of  leading  the  pupil  to  reason 
for  himself  and  draw  his  own  inferences  from  the  common 
phenomena  about  him. 

The  author  takes  pleasure  in  acknowledging  here  the 
many  obligations  due  to  Dr.  C.  O.  Townsend  of  the  United 
States  Department  of  Agriculture  for  his  very  effective 
assistance  in  revising  the  manuscript  of  this  work ;  also  to 
Professor  Charles  Wright  Dodge  of  the  University  of 
Rochester,  and  Professor  W.  F.  Ganong  of  Smith  College 
for  valuable  criticisms  and  suggestions.  Acknowledg- 
ments are  also  due  to  Messrs.  D.  Appleton  and  Company, 
for  permission  to  use  illustrations  from  Coulter's  "Plant 
Relations"  and  "Plant  Structures,"  copyright,  1899,  and 
to  the  owners  of  Gray's  Botanies,  to  Professor  William 
Trelease  of  the  Missouri  Botanical  Garden,  to  Mr. 
Gifford  Pinchot  of  the  United  States  Department  of 
Agriculture,  and  to  Mr.  W.  S.  Bailey  of  the  Chautauqua 
Bureau  of  Publication,  for  permission  to  reproduce  illus- 
trations from  their  publications.  Quite  a  number  of  the 
figures  used  are  from  original  drawings  by  pupils  of  the 
Washington,  Ga.,  High  School. 


CONTENTS 


PAGE 

I.   INTRODUCTION 9 

II.  THE  LEAF:  ITS  USES  —  Transpiration;  Respiration  and 
Food  Production;  The  Typical  Leaf  and  its  Parts; 
Veining  ;  Branched  Leaves  ;  Phyllotaxy,  or  Leaf  Ar- 
rangement;  Leaf  Adjustment;  Transformations  of 
Leaves;  Field  Work 15 

III.  FRUITS  —  Fleshy  Fruits;  Dry  Fruits;  Dehiscent  Fruits; 
Accessory,  Aggregate,  and  Collective  Fruits ;  Field 
Work 63 

IV.  SEEDS  AND  SEEDLINGS  —  Monocotyledons  and  Polycoty- 
ledons  ;  Dicotyledons  ;  Forms  and  Growth  of  Seed ; 
Germination ;  Seedlings  ;  Growth  ;  Field  Work  .  87 

V.  ROOTS  AND  UNDERGROUND  STEMS  —  Function  and  Struc- 
ture of  Roots  ;  Fleshy  Roots ;  Sub-aerial  Roots ; 
Underground  Stems  ;  Plant  Food  ;  Field  Work  .  .  120 

VI.  THE  STEM  PROPER — Stem  Forms  and  Uses;  Stems  of 

Monocotyledons ;  Stems  of  Dicotyledons  ;  Movement 
of  Water  through  the  Stem ;  Wood  Structure ;  Field 
Work 142 

VII.  BUDS  AND  BRANCHES  —  Branching  Stems  ;  Buds;  Inflor-   ~ 

escence;  Field  Work 173 

VIII.  THE  FLOWER  —  Hypogynous  Monocotyledons  ;  Epigynous 
Monocotyledons  ;  Dicotyledons  ;  The  Corolla ;  Suppres- 
sions, Alterations,  and  Appendages  ;  Nature  and  Office 
of  the  Flower ;  Pollination  ;  Field  Work  ...  196 

IX.   ECOLOGY  — Ecological  Factors:    Plant  Societies:    Field 

Work 237 

7 


8  CONTENTS 

PAGE 

X.   SEEDLESS  PLANTS — Their  Place  in  Nature  ;  Fern  Plants  ; 

Study  of  a  Bryophyte ;  The  Algas 250 

XI.    FUNGI  —  Their  Classification  ;  Mushrooms;  Rusts;  Field 

Work 271 

SYSTEMATIC  BOTANY 286 

APPENDIX 289 

INDEX 297 


BOTANY  ALL   THE  YEAR    ROUND 


I.    INTRODUCTION 

2104-8 

1.  General  Statement.  —  Botany   is   the   science  which 
treats  of  the  vegetable  kingdom,  but  the  subject  is  so  com- 
prehensive that  it  has  been  divided  into  many  branches, 
each  of  which  is  a  science  in  itself.     For  instance,  there 
are  Mycology,  the  study  of  mushrooms  and  other  fungi ; 
Bacteriology,    the   study    of   the    microscopic   forms   con- 
cerned  in   the  process  of   fermentation,  and  in  the  pro- 
duction of  disease ;  Paleobotany,  the  study  of  fossil  plants 
—  and  many  others,  with  which  we  have  no  concern  at 
present.     Each   of   these   studies    may   be   viewed   under 
various  aspects,  and  these  in  turn  have  given  rise  to  still 
other  divisions  of  the  subject,  such  as,  — 

2.  Morphology,  or  Structural  Botany,  the  study  of  the 
different  organs  or  parts  of  plants  in  regard  to  their  form 
and  uses  and  the  various  changes   and  adaptations  they 
may  undergo. 

3.  Histology,  or  Plant  Anatomy,  the  microscopic  study 
of  the  minute  structure  of  plant  organs.     This  can  not  be 
carried  on  well  without  the  use  of  the  compound  micro- 
scope and  other  appliances  not  obtainable  in  many  schools. 
Something,  however,  may  be  learned  from  a  few  simple  ex- 
periments, accompanied  by  intelligent  observation  with  a 
hand  lens,  and  it  is  only  in  so  far  as  it  can  be  carried  on 
by  ordinary  means  like  these,  that  this  branch  of  the  sub- 
ject is  touched  upon  in  the  present  work. 

9 


I0  INTRODUCTION 

4.  Vegetable  Physiology,  the  study  of  the  action  of  liv- 
ing plants  and  their  organs,  their  mode  of  growth  and  re- 
production, and  their  various  movements  for   adjustment 
to  their  surroundings,  as   the   attraction  of   roots  toward 
moisture  and  of  leaves  toward  light. 

5.  Ecology,  the  study  of  plants  in  their  relations  to  ex- 
ternal conditions,  or,  tq  use  a  more  convenient  term,  their 
environment.     This   is   one  of   the   most   interesting  and 
important  of  all  the  departments  of  botany,  and  presents 
many  points  of  direct  practical  concern  to  the  farmer. 

6.  Taxonomy,   c'alled    also    Systematic    or    Descriptive 
Botany,  the  study  of  plants  in  their  relationships  to  one 
another.    Its  work  is  to  note  their  resemblances  and  differ- 
ences,  and   by  means   of   these  to   classify  or   distribute 
them  into  certain  great  groups  called  families  or  orders, 
and  these  again  iato  lesser  groups  of  genera  and  species. 
This  work   of   classification  was  formerly  considered   the 
chief  end  of  the  study  of  botany,  which  thus  too  often  de- 
generated into  a  mere  mechanical  drill  in  hunting  down 
plants   and   labeling   them  with    hard  names.      The   ten- 
dency at   present  is   to   ignore   this  part  of   the   subject 
altogether,  which  is  nearly  as  great  a  mistake  as  the  old- 
fashioned  error  of  thinking  that  the  study  of  botany  con- 
sisted  merely  in  learning  a  string  of  hard  words.     One  of 
the  chief  pleasures  to  be  derived  from  botanical  studies, 
for  most  of  us,  consists  in  being  able  to  know  and  recog- 
nize the  various  plants  we  meet  with.     The  first  thing  we 
all  ask  on  seeing  a  new  shrub  or  flower  is,  "What  is  it  ? " 
and  this  question  can  be  answered  satisfactorily  only  by 
referring  each  to  its  proper  class  or  order. 

7.  Learn  to  know  the  Common  Plants.  —  These  five  sub- 
divisions make  up  the  study  of  botany,  as  generally  taught 
in  the  schools.  They  apply  to  all  plants,  and  the  only 
practicable  way  for  most  of  us  to  learn  them  is  by  a  study 
of  the  common  vegetable  life  about  us. 


INTRODUCTION  II 

8.  Definitions.  —  "Organ"  is  a  general  name1  for  any 
part  of  a  living  thing,  whether  animal  or  vegetable,  set 
apart  to  do  a  certain  work,  as  the  heart  for  pumping  blood, 
the  lungs  for  breathing,  or  the  stem  and  leaves  of  a  plant 
for  conveying  and  digesting  the  sap.     By  "  function  "  is 
meant  the  work  or  office  that  an  organ  has  to  perform. 

9.  The  Cell.  —  In  its  strictly  scientific  sense  this  word  is 
applied  to  the  smallest  portions  of  organized  matter  that 
go  to  make  up  a  living  body,  whether  vegetable  or  animal. 
It  usually  consists  of  a  tiny  membra- 

nous sac  lined  with  a  living  semifluid 
substance  called  protoplasm,  which 
ordinarily  has  one  portion  of  denser 
consistency  than  the  rest,  called  the 
nucleus.  Within  the  protoplasmic 
lining  are  contained  various  watery 
fluids  known  as  cell  sap.  These  little 
sacs  are  packed  together  to  build  up 
the  vegetable  or  animal  structure  as 
bricks  are  in  building  a  wall.  They  i.—  Typical  ceils:  «,nu- 


are  of  various  sizes  and  shapes.    The  ™'  w' 

containing   membrane   is   called   the 

cell  wall.  Cells  can  exist,  however,  without  any  wall,  as 
mere  specks  or  globules  of  protoplasm,  but  these  are  not 
common  in  vegetable  structures.  The  essential  part  of 
every  cell  is  the  protoplasm  with  its  nucleus.  This  sub- 
stance, so  far  as  we  know  at  present,  constitutes  the  physi- 
cal basis  of  all  life,  and  if  the  protoplasm  loses  its  vitality, 
the  cell  dies  and  can  no  longer  perform  its  functions  of 
absorbing  and  retaining  liquids.  Slice  a  fresh  beet  in  a 
vessel  of  water  and  a  boiled  one  in  another;  how  is  the 
liquid  affected  in  each  ?  Account  for  the  difference. 

The  name  "  cell  "  is  also  applied  to  the  compartments 
into  which  the  fruits  and  seed  vessels  of  many  plants  are 
divided.  This  double  meaning  of  an  important  term  is 
unfortunate,  but  the  context  will  always  show  in  which 
sense  it  is  to  be  taken,  so  that  no  confusion  need  result. 


I2  INTRODUCTION 

10.  Tissue  is  a  term  used  to  denote  any  animal  or  vege- 
table substance  that  is  composed  of  a  particular  kind  of 
material  and  that  performs  a  particular  office  or  function. 
Thus,  for  instance,  we   have   bony  tissue  and   muscular 
tissue  in  animals;  that  is,  tissue  made  of  bone  substance 
and  of  muscle  substance  and  doing  the  work  of  bone  and 
muscle  respectively.     So  in  plants,  we  have  woody  tissue, 
or  tissue  made  of  woody  substance,  and  vascular  tissue,  or 
tissue  made  up  of   little  conducting  vessels,  which   have 
their  especial  functions  to  perform. 

11.  Appliances  needed  for  General  Use.  —  The  only  appli- 
ances necessary  for  the  study  of   this  book,  besides  the 
material  furnished  by  the  woods  and  fields  about  us,  are 
so  few  and  simple  that  there  can  be  no  difficulty  in  pro- 
viding them.     The  following  list  comprises  about  all  that 
are  essential :  — 

Half  a  dozen  glass  jars ;  preserve  jars  or  wide-mouthed 
bottles  will  answer. 

Half  a  dozen  soup  plates  or  other  shallow  dishes  for 
germinators. 

Some  good-sized  bits  of  window  glass  for  covering  jars 
and  dishes. 

A  garden  trowel. 

A  good  hatchet  for  use  when  the  study  of  timber  is 
taken  up. 

A  very  sharp  knife  — a  razor  is  better,  if  it  can  be 
obtained  —  for  making  sections. 

A  small  whetstone  for  sharpening  knives. 

A  vial  of  tincture  of  iodine. 

A  pint  of  red  ink ;  or,  if  preferred,  a  good  coloring  fluid 
can  be  made  by  purchasing  an  ounce  or  two  of  eosin  from 
the  druggist  and  mixing  it  with  water. 

A  pot  of  photograph   paste. 

If  a  yard  or  two  of  India  rubber  tubing,  a  common  bulb 
thermometer,  and  a  pair  of  druggist's  scales  are  added  to 
the  above  list,  the  number  of  experiments  that  can  be  per- 
formed will  be  considerably  increased. 


INTRODUCTION  13 

12.  Appliances  for  Individual  Use.  —  In  addition  to  the 
general  outfit  for  the  school,  each  pupil   should  be  pro- 
vided with  — 

A  good  penknife. 

A  drawing  book  (or  drawing  paper)  and  a  blank  book 
for  taking  notes. 

A  book  for  dried  specimens,  made  by  sewing  together 
two  or  three  sheets  of  unsized  paper,  such  as  newspapers 
are  printed  on ;  this  can  be  purchased  from  a  printer. 

Two  well-pointed  pencils,  one  hard,  the  other  medium. 

A  pair  of  dissecting  needles ;  wax-headed  steel  pins  will 
do,  but  better  ones  can  be  made  by  running  the  heads  of 
ordinary  sewing  needles  into  handles  of  soft  wood  and 
gluing  them  in. 

Two  bits  of  glass,  not  larger  than  a  visiting  card,  as 
thin  and  clear  as  can  be  obtained,  for  inclosing  specimens 
that  must  be  held  up  to  the  light  for  examination.  The 
glass  plates  sold  for  photograph  negatives  serve  well  for 
this  purpose. 

A  good  hand  lens.  The  glasses  known  as  "  linen 
testers "  can  be  purchased  for  twenty-five  cents  apiece, 
and  make  very  good  magnifiers. 

A  special  place  ought  to  be  provided  in  the  schoolroom 
for  storing  all  these  articles,  and  the  strictest  order  exacted 
in  the  care  of  them.  They  should  always  be  ready  when 
wanted,  and  never  used  for  any  other  purpose. 

13.  Living  Material.  —  A  number  of  potted  plants  should 
always  be  kept  in  the  schoolroom,  especially  in  cities,  for 
observation  and  experiment.     Among  those  recommended 
for  this  purpose  are  the  following  :  — 

One  or  two  ferns. 

A  calla  lily,  or  other  arum. 

A  young  India  rubber  tree  (Ficits  elastica). 

A  pot  of  "  wandering  Jew  "  (Zebrina  penduld).  The 
plain,  green-leaved  varieties  are  best. 

Some  kind  of  prickly  cactus.  The  common  prickly  pear 
(Opuntid)  and  the  Mamillaria  make  good  specimens. 


INTRODUCTION 


A  sedge ;  the  umbrella  plant  (Cyperus  alternifolius)  or 
the  Egyptian  paper  plant  (C.  papyrus},  so  common  in 
greenhouses,  will  either  of  them  do  very  well,  though  our 
native  wild  plants  are  always  preferable  when  they  can  be 
obtained. 

Healthy  plants  of  oxalis  and  tropaeolum. 

A  twining  vine ;  hop,  morning  glory,  kidney  bean,  etc. 

A  glass  jar  with  one  or  two  water  plants,  such  as  pond- 
weed  (Potamogeton},  hornwort  (Ceratophyllum\  bladdervvort 
(Utricularia\  or  pickerel  weed  (Pontederia),  etc. 


ENGLISH  SCALE, 
FOUR  INCHES 


METRIC  SCALE, 
TEN  CENTIMETERS 


2.— A  comparative  scale  of  the  English  and 
metric  systems  of  length  measure.  One  decimeter 
=  10  centimeters  =  100  millimeters  =  approximately 
4  inches.  — 


3- — A  comparative 
scale  of  the  Centigrade 
and  Fahrenheit  ther- 
mometers. On  the  Cen- 
tigrade scale  o  =  the 
temperature  of  melting 
ice,  and  ICCP  =  that  of 
boiling  water. 


II.   THE  LEAF:    ITS  USES 

TRANSPIRATION 

MATERIAL.  —  Freshly  cut  sprigs  of  various  kinds,  bearing  healthy 
leaves  ;  a  leaf  of  the  white  garden  lily  (L.  candiduni)  or  of  the  wander- 
ing Jew  (Zebrina  pendula) ;  two  hermetically  sealing  preserve  jars ;  a 
little  beeswax  or  tin  foil ;  a  bit  of  looking  glass ;  a  number  of  empty 
bottles  with  perforated  stoppers  or  rubber  cloth  covers. 

NOTE.  —  In  order  to  avoid  cumbering  the  pages  of  the  text  with  tech- 
nical nomenclature,  botanical  names  of  specimens  mentioned  will  be 
given  only :  First,  in  the  case  of  foreign  or  little  known  species ; 
Second,  where  the  popular  name  is  local  or  provincial,  or  where  the 
same  term  is  applied  to  several  different  plants ;  and  Third,  where 
special  accuracy  of  designation  is  required. 

14.  Why   Leaves   wither.  —  Dry   two    self-sealing    jars 
thoroughly,  by  holding  them  over  a  stove  or  a  lighted  lamp 
for  a  short  time  to  prevent  their  "  sweating."     Place  in  one 
a  freshly  cut  leafy  sprig  of  any  kind,  leaving  the  other 
empty.     Seal  both  jars  and  set  them  in  the  shade.     Place 
beside  them,  but  without  covering  of  any  kind,  a  twig  simi- 
lar to  the  one  in  the  jar.     Both  twigs  should  have  been 
cut  at  the  same  time,  and  their  cut  ends  covered  with  wax 
or  vaseline,  to  prevent  access  of  air.     At  the  end  of  six 
or  eight   hours   look  to   see  if  there  is  any  moisture   de- 
posited on  the  inside  of  either  jar.     If  there  is  none,  set 
them  both  in  a  refrigerator  or  other  cool  place,  for  half 
an  hour,  and  then  examine  them  again.     On  which  jar  is 
there  a  greater  deposit  of  dew  ?     How  do  you  account  for 
it?     Take  the  twig  out  of  the  jar  and  compare  its  leaves 
with  those  of  the  one  left  outside;  which  have  withered 
most,  and  why  ? 

15.  Transpiration. — We    learn    from    experiments   like 
the  foregoing  that  one  office  of  leaves  is  transpiration,  or 

15 


i6 


THE   LEAF 


the  giving  off  of  moisture,  just  as  animals  do  through  the 
pores  of  the  skin.1  Now,  we  all  know  what  happens  to  us 
if  the  perspiration  glands  of  our  body  get  stopped  up,  and 
hence  we  need  not  be  surprised  if  hedgerows  can  not  be 
kept  vigorous  and  healthy  by  dusty  roadsides,  nor  if  even 
sturdy  trees  and  shrubs  take  on  a  sickly  look  when  the 
summer  rain  delays  too  long  to  give  them  their  accus- 
tomed bath. 


16.  Stomata. — The  transpiration  pores  of  leaves  are 
called  stomata  (sing,  stoma)  from  a  Greek  word  meaning 
"  mouths."  Generally  they  are  too  small  to  be  seen  with- 
out a  compound  microscope,  but  their  presence  can  be 
made  manifest  by  a  simple  experiment.  Place  a  bit  of 
looking  glass  against  your  cheek  or  your  arm  on  a  warm 
day,  and  it  will  soon  be  covered  with  a  film  of  moisture 
from  the  skin.  Next,  place  the  glass  in  contact  with  the 
under  side  of  a  healthy  growing  leaf  for  thirty  to  forty-five 
minutes,  and  see  if  you  can  detect  any  moisture  on  it. 
The  deposit  'will  probably  be  fainter  than  that  from  the 
skin,  but  the  presence  of  any  at  all  will  show  that  the  leaf 
transpires. 

There  are  a  few  plants,  such  as  the 
white  lily  of  the  gardens  (L.  candiduni} 
and  the  wandering  Jew,  in  which  the 
stomata  are  large  enough  to  be  seen 
with  a  hand  lens. 
4.— Portion  of  the  The  common  iris  also 

epidermis  of  the  gar-      shows     them,     though 

den     balsam,     highly 

magnified,  showing  the      nOt      SO      distinctly. 

Strip    off    from    the 
under  side  of  such  a 


very  sinuous  walled 
epidermis  cells  and 
three  stomata  (after 
GRAY). 


5,  6.  —  Stomata    of 


leaf  a  portion  of  the    whiie  Iily  leaf :  5- closed: 

•  i  .  6,  open  (GRAY). 

epidermis,  or  outer  covering.     Place  it 

between  two  bits  of  glass  with  the  outside  uppermost,  and 

1  Transpiration,  though  similar  in  external  effects  to  the  perspiration  of  ani- 
mals, must  not  be  confounded  with  it,  as  the  two  functions  are  physiologically 
quite  different 


TRANSPIRATION 


7.— Stomata  of  an  oak  leaf:  A,  a  small  piece 
(highly  magnified)  of  under  epidermis  removed 
to  show  stomata,  g,  and  minute  hairs,  h.  B,  a 
stoma  in  vertical  median  section,  cut  at  right  angles 
to  its  longer  axis ;  a,  intercellular  space ;  g,  guard 
cell ;  s,  orifice  of  stoma. 


examine  it  with  a  good  lens.  Hundreds  of  little  eye-shaped 
dots  will  be  seen  covering  the  surface,  which  can  easily 
be  recognized,  by 
comparison  with  the 
accompanying  Fig- 
ures, as  stomata.  i  w^uj^V-W  -IT 
Examine  a  portion  ^ 
of  the  epidermis 
from  the  upper  side 
of  the  leaf ;  are  the 
stomata  distributed 
equally  on  both  sides, 
and  if  not,  on  which 
are  they  thickest  ? 
Which  side  of  the  epidermis  seems  to  be  most  active  in  the 
work  of  transpiration  ? 

17.  Distribution  of  Stomata. — While  stomata  are  gen- 
erally most  abundant  on  the  under  side  of  leaves,  where 
they  are    protected   from   excessive   light  and  heat,   this 
is  not  always  the  case.      Similar  openings  occur  also  on 
young  stems,  and  are  called  lenticels.     In  vertical  leaves, 
like  those  of  the  iris,  which  have  both  sides  equally  ex- 
posed to  the  sun,  stomata  are  distributed  equally  on  both 
sides.     In  plants  like  the  water  lily,  where  the  under  sur- 
face   lies   upon   the  water,  making    transpiration  in  that 
direction  impossible,  they  occur  only  on  the  upper  side. 
Succulent  leaves,  as  a  general  thing,  have  very  few,  be- 
cause they  need  to  conserve  all  their  moisture.     Submerged 
leaves  have  none  at  all ;  can  you  tell  why  ? 

18.  Protection  of  Stomata.  —  In  addition  to  their  function 
of  transpiration,  stomata  permit  the  entrance  to  the  interior 
of  the  plant  of  atmospheric  air  containing  carbon  dioxide, 
a  gaseous  substance  used  by  them  in  the  formation  of  food. 
If  they  become  choked  up  with  water  or  other  obstruction, 
the  leaves  can  neither  exhale  their  superfluous   moisture 
nor    take   in   air;    hence   these   pores   are    protected   by 
hairs,  wax,  and  other  water-shedding  appendages.     Plunge 

ANDREWS'S   BOT.  —  2 


rg  THE   LEAF 

a  sprig  of  the  dwarf  St.  John's-wort  (Hypericum  mutilum) 
or  of  wandering  Jew  into  water  and  notice  the  silvery 
appearance  of  the  leaves,  especially  on  the  under  side. 
In  the  iris  it  is  the  same  on  both  sides ;  why  ?  Remove 
the  sprig  from  the  water,  and  the  leaves  will  be  perfectly 
dry.  In  the  wandering  Jew,  as  may  be  seen  with  a  good 
hand  lens,  this  is  due  to  the  air  imprisoned  by  little  mem- 
branous appendages  which  surround  the  stomata  and  pre- 
vent the  water  from  entering.  In  other  cases,  as  cabbage, 
hypericum,  etc.,  a  coating  of  wax  protects  the  transpiration 
pores,  and  it  is  the  reflection  of  the  light  from  the  air 
entangled  in  these  protective  coverings  that  gives  the 
leaves  their  silvery  appearance  under  water. 

19.  Amount  of  Transpiration.  —  Few  people  have  any 
idea  of  the  enormous  amount  of  water  given  off  by  leaves. 
It  has  been  calculated1  that  an  oak  may  have  700,000 
leaves  and  that  111,225  kilograms  of  water  (about  244,695 
Ibs.)  may  pass  from  its  surface  in  the  five  active  months 
from  June  to  October,  and  226  times  its  own  weight  of 
water  may  pass  through  it  in  a  year.  If  this  seems  an 
extravagant  estimate,  we  can  easily  make  one  for  our- 
selves. 

Fill  three  bottles  with  water,  and  cover  them  tightly  with 
rubber  cloth  to  prevent  evaporation.  Mark  the  point  at 
which  the  water  stands  in  the  bottles,  make  a  small 
puncture  through  the  covers,  and  insert  into  one  bottle 
the  end  of  a  healthy  twig  of  peach  or  cherry,  into  the 
second  a  twig  of  catalpa,  grape,  or  any  other  large-leaved 
plant,  and  into  the  third,  one  of  magnolia,  holly,  or  other 
thick,  tough-leaved  evergreen,  letting  the  stems  of  all  reach 
down  well  into  the  water.  Care  must  be  taken  to  select 
twigs  of  the  same  age,  as  the  absorbent  properties  of  very 
young  stems  are  more  injured  by  cutting  and  exposure  than 
those  of  older  ones.  All  the  specimens  should  be  cut  under 
water  if  possible,  as  even  an  instant's  exposure  to  the  air 
will  greatly  diminish  the  activity  of  the  cut  surface.  Peach 

1  See  Marshall  Ward,  "The  Oak." 


TRANSPIRATION  19 

is  an  excellent  plant  to  experiment  with,  as  its  woody  twigs 
are  not  greatly  affected  by  cutting,  and  it  absorbs  water 
almost  as  rapidly  as  it  transpires.  At  the  end  of  twenty- 
four  hours  note  the  quantity  of  liquid  that  has  disappeared 
from  each  glass.  This  will  represent  approximately  the 
amount  absorbed  by  the  leaves  from  the  twigs  to  replace 
that  lost  by  transpiration.  Which  twig  has  transpired 
most  ?  Which  least  ?  Note  the  condition  of  the  leaves 
on  the  different  twigs  ;  have  they  all  absorbed  water  as 
rapidly  as  they  have  lost  it  ?  How  do  you  know  this  ? 
Pluck  the  leaves  from  each  twig,  one  by  one,  lay  them  on 
a  fiat  surface  that  has  been  previously  measured  off  by  the 
aid  of  a  rule,  into  a  square  of  about  thirty  centimeters 
(twelve  inches)  to  a  side,  containing  nine  hundred  square 
centimeters  (one  hundred  forty-four  square  inches),  and 
thus  form  a  rough  estimate  of  the  area  covered  by  each 
specimen.  Measure  the  amount  of  water  transpired  by 
filling  up  each  bottle  to  the  original  level,  from  a  common 
medicine  glass,  or  if  this  cannot  be  obtained,  use  a  table 
spoon,  counting  two  spoonfuls  to  the  ounce.  Make  the 
best  estimate  you  can  of  the  number  of  leaves  on  each  tree, 
and  calculate  the  number  of  kilograms  (or  pounds)  of  water 
it  would  give  off  at  that  rate  in  a  day.  In  one  experiment 
a  peach  twig  containing  thirty-one  leaves  gave  off  three- 
quarters  of  an  ounce  of  water  in  twenty -four  hours ;  how 
many  pounds  would  that  be  for  the  tree,  estimating  it  to 
bear  eighteen  thousand  leaves  ?  As  the  tissues  of  a  grow- 
ing plant  are  much  more  active  than  those  of  a  severed 
branch,  calculations  of  this  kind  are  not  likely  to  exceed 
the  truth,  even  when  we  take  into  consideration  the  fact 
that  the  twig  in  the  experiment  has  unlimited  water,  which 
the  roots  of  a  growing  plant  have  not  always. 

These  experiments  may  be  varied  at  the  option  of  the 
teacher  as  time  and  opportunity  may  permit,  so  as  to  test 
the  absorbing  and  transpiring  properties  of  any  number  of 
plants  or  of  the  same  plant  at  different  stages  of  growth. 
They  will  succeed  best  in  dry,  warm  weather,  as  the  work 
of  transpiration  is  then  most  active. 


20  THE   LEAF 

20.  Practical  Effects  of  Transpiration.  —  Where  does  all 
this  moisture  come  from  ?     If  the  water  in  the  last  experi- 
ment is  colored  with  a  little  eosin   or  with    red   ink,    its 
course  can  be  traced  through  the  stem  into  the  leaves.     In 
growing  plants  the  earth  takes  the  place  of  our  tumbler  of 
water,  and  from  it  the  moisture  is  drawn  up  by  the  roots 
and  conveyed  through  the  stem  to  the  leaves.     Thus  we  see 
that  trees  are  constantly  acting  as  great  pumps,  drawing 
up  water  from  the  lower  strata  of  the  soil  and  distributing 
it  to  the  thirsty  air  in  summer.     As  the  water  given  off 
by  transpiration  is  in  the  form  of  vapor,  it  must  draw  from 
the  plant  the  amount  of  heat  necessary  for  its  vaporization, 
and  hence  it  has  the  effect  of  making  the  leaves  and  the  air 
in  contact  with  them  cooler  than  the  surrounding  medium. 

21.  The    Cause    of    Transpiration.  —  The    reason    why 
plants  exhale  such  large  quantities  of  water  is  because  they 
get  part  of  their  food  from  mineral  and  other  substances 
dissolved  in  the  water  of  the  soil,  but  this  food  is  in  such  a 
diluted  state  that  enormous  quantities  of  the  liquid  contain- 
ing it  must  be  taken  up  in  order  to  give  the  plant  the  nour- 
ishment it  requires.     This  liquid  travels  through  the  stem 
as  sap,  and  after  all  the  food  substance  has  been  extracted, 
the  waste  water  is  exhaled  by  the  leaves.     Sometimes  the 
roots  absorb  moisture  faster  than  the  leaves  can  transpire 
it ;  the  water  then  exudes  through  the  stomata  and  settles 
in  drops  on  the  blade,  causing  the  leaves  to  sweat,  just 
as  our  bodies  do  under  similar  conditions.     Sometimes,  on 
the  other  hand,  the  leaves  transpire  faster  than  the  roots 
can  absorb,  and  then  the  plant  wilts. 

PRACTICAL  QUESTIONS 

1.  Do  you  see  any  connection  between  the  facts  just  stated  and  the 
stories  of  "  weeping  trees "  and  "  rain  trees  "  that  we  sometimes  read 
about  in  the  papers  ?     (Section  21.) 

2.  Can  you  explain  the  fact  sometimes  noticed  by  farmers,  that  in 
wooded  districts,  springs  which  have  failed  or  run  low  during  a  dry 
spell   sometimes  begin  to  flow  again  in  autumn  when  the  trees  drop 
their  leaves,  even  though  there  has  been  no  rain?     (19,  20.) 


RESPIRATION    AND   FOOD    PRODUCTION  21 

3.  Other  things  being  equal,  which  would  have  the  cooler,  pleasanter 
atmosphere  in  summer,  a  well-wooded  region  or  a  treeless  one?     (20.) 

4.  Could  you  keep  a  bouquet  fresh  by  giving  it  plenty   of  fresh 
air?     (14). 

5.  Why  does  a  withered  leaf  become  soft  and  flabby,  and  a  dried 
one  hard  and  brittle?    (9,  14.) 

6.  Why  do   large-leaved  plants,  as   a  general   thing,  wither  more 
quickly  than  those  with  small  leaves?     (14-19.) 

7.  Is  the  amount  of  water  absorbed  always  a  correct  indication  of 
the  amount  transpired  ?     Explain.     (20,  21.) 

8.  Why  must  the  leaves  of  house  plants  be  washed  occasionally  to 
keep  them  healthy?     (15-18.) 

9.  Why  is  it  so  hard  to  get  trees  to  live  in  a  large  manufacturing 
town?      (15,  1 8.) 

RESPIRATION  AND  FOOD   PRODUCTION 

MATERIAL.  —  A  green  aquatic  plant  of  some  kind  in  a  glass  of  water ; 
two  wide-mouthed  glass  jars ;  a  bent  glass  or  rubber  tube,  and  a  shallow 
dish  of  water ;  boiled  bean  or  tropaeolum,  or  other  green  leaves  ;  a  half 
pint  of  alcohol ;  some  tincture  of  iodine  ;  a  strip  or  two  of  tin  foil. 

22.  Leaves  give  off  Oxygen.  —  Place  in  a  glass  of  water 
a  green  aquatic  plant  of  any  kind ;  the  common  brook 
silk  (Spirogyra)  found  in  almost  every  pool  will  answer. 
Set  it  in  the  sunlight  and  place  beside  it  another  similar 
vessel  containing  nothing  but  water,  and  also  a  third  ves- 
sel containing  a  piece  of  the  same  plant  immersed  in  water 
from  which  the  air  has  been  expelled  by  boiling.  After  a 
time  bubbles  will  be  seen  rising  from  the  first  vessel.  Air 
bubbles  will  usually  form  on  the  bottom  and  sides  also, 
but  these  are  caused  by  the  expansion  of  gases  contained 
in  the  liquid,  as  will  be  evident  on  comparing  them  with 
similar  phenomena  in  the  jar  containing  only  water,  and 
must  not  be  confounded  with  the  gas  given  off  by  the 
plant.  Remove  the  vessel  from  the  light,  and  the  bubbles 
will  soon  cease  to  appear,  but  will  begin  to  form  again  if 
restored  to  the  sunshine,  thus  showing  that  their  produc- 
tion can  take  place  only  in  the  light.  Do  any  bubbles  at 
all  appear  in  the  glass  with  the  boiled  water  ? 

It  has  been  proved  by  chemical  analysis  that  these 
bubbles  are  oxygen,  which  the  plant  has  been  separating 


22  THE    LEAF 

from  the  gases  mixed  with  the  water,  and  giving  off.  It 
is  even  more  active  in  separating  oxygen  from  the  air,  but 
the  process  is  not  visible  to  the  eye,  because  we  cannot  see 
a  gas  except  in  the  form  of  bubbles.  Water  is  used  not 
as  an  aid  to  the  plant  in  the  performance  of  its  function, 
but  in  order  to  enable  us  to  see  the  result. 

23.  Leaves  as  Purifiers  of  the  Atmosphere.  —  Fill  two 
tumblers  with  water,  to  expel  the  air,  and  invert  in  a 
shallow  dish  of  water,  having  first  introduced  a  freshly 
cut  sprig  of  some  healthy  green  plant  into  one  of  them. 
Then  by  means  of  a  bent  tube  blow 
into  the  mouth  of  each  tumbler 
till  all  the  water  is  expelled  by  the 
impure  air  from  the  lungs.  Set 
the  dish  in  the  sunshine  and  leave 
showing  it,  taking  care  that  the  end  of  the 
how  leaves  pudfy  the  atmos-  cutting  is  in  the  water  of  the  dish. 
After  forty-eight  hours  remove  the 

tumblers  by  running  under  the  mouth  of  each,  before  lift- 
ing' from  the  dish,  a  piece  of  glass  well  coated  with  vase- 
line (lard  will  answer)  and  pressing  it  down  tight  so  that  no 
air  can  enter.  Place  the  tumblers  in  an  upright  position, 
keeping  them  securely  covered.  Fasten  a  lighted  taper 
or  match  to  the  end  of  a  wire,  plunge  it  quickly  first  into 
one  tumbler,  then  into  the  other,  and  note  the  result.  It 
is  an  established  fact  that  a  light  will  not  burn  in  an 
impure  atmosphere ;  this  is  why  well  cleaners  send  down 
a  lighted  candle  before  going  into  a  well  themselves. 
What  are  we  to  infer  from  the  effects  observed  as  to  the 
action  of  the  plant  upon  the  atmosphere  ? 

This  experiment  will  not  succeed  unless  performed  very 
carefully,  and  the  air  must  be  absolutely  excluded  from 
the  tumblers  until  the  instant  the  taper  is  plunged  in. 

24.  Leaves  as  Food  Makers. —  It  thus  appears  that 
plants  are  constantly  reversing  the  effects  of  animal  res- 
piration by  giving  off  oxygen  and  absorbing  carbon  dioxide 
from  the  air.  Besides  acting  as  digestive  and  assimilating 


RESPIRATION   AND  FOOD   PRODUCTION  23 

organs,  leaves  are  the  laboratories  in  which  plant  food 
is  manufactured  out  of  the  crude  materials  brought  up 
from  the  soil  by  the  sap,  and  those  absorbed  through  the 
stomata  from  the  gases  of  the  atmosphere.  Carbon  di- 
oxide taken  from  the  atmosphere  is  somehow  used  up  in 
this  operation,  and  the  oxygen,  which  is  not  needed  by 
the  plant,  is  given  back  to  be  consumed  by  animals.  This 
is  the  most  important  work  the  leaf  has  to  do,  and  because 
it  can  take  place  only  in  the  light,  has  been  named  by 
botanists  Photosynthesis^  a  word  which  means  "  building 
up  by  means  of  light,"  just  as  photography  means  "drawing 
or  engraving  by  means  of  light." 

25.  Why  Leaves   are   Green.  —  Has   the   color   of   the 
leaf  anything  to  do  with  this  function  ?     It  will  help  to  a 
correct  answer  if  we  remember  that  herbs  grown  in  the 
dark,    and   parasites   like   the   dodder    and    beech   drops 
(Epiphegus\    which    steal    their    food   ready   made   from 
the  tissues  of  other  plants,  and  so  have  no  need  to  manu- 
facture it  for  themselves,   always  lose  their  green  color. 
Place  a  seedling  of  oats  or  other  rapidly  growing  shoot  in 
the  dark  for  a  few  days  and  note  its  loss  of  color.     Leave 
it  in  the  dark  indefinitely,  and  it  will  lose  all  color  and  die. 
Hence  we  may  conclude  that  there  is  some  intimate  con- 
nection between  the  action  of  light  and  the  green  coloring 
matter  of  leaves.     This  green  matter  is  called  Chlorophyll, 
a  word  meaning  "  leaf  green,"  and   physiologists  tell  us 
that  through  its  agency  the  crude  substances  brought  up 
from  the  soil  in  the  sap  and  the  carbon  dioxide  of  the  air 
are  converted  into  nourishment. 

26.  Starch  as  Plant  Food.  —  It  is  the  office  of  chloro- 
phyll to  manufacture  a  particular  class   of    plant   foods 
known  as  carbohydrates.     The  commonest  and  most  impor- 
tant of  these  is  starch,  the  presence  of  which  can  generally 
be  detected  without  much  difficulty.     Boil  a  few  leaves  of 
bean  or  sunflower,  tropaeolum,  etc.,  for  about  fifteen  min- 
utes, and  soak  them  in  alcohol  until  all  the  chlorophyll  is 
dissolved  out.     Rinse  them  in  water,  and  soak  the  leaves 


24  THE   LEAF 

thus  treated,  in  a  weak  solution  of  iodine  for  half  an  hour ; 

then  wash  them  and  hold  them  up  to  the  light.  Iodine 
turns  starch  blue;  hence  if  there 
are  any  blue  spots  on  the  leaves, 
what  are  you  to  conclude  ?  Other 
food  substances  can  be  detected 
by  proper  tests,  but  none  of  them 
so  readily  as  starch. 

27.  Necessity  of  Light  and  Air. 
—  Exclude  the  light  from  parts  of 
healthy  leaves  on  a  growing  plant 
of  tropaeolum,  bean,  etc.,  by  plac- 

9~-Leaf  arranged  with  a      ™8   bands    °r    PatcheS     °f.  ***    f°U 

piece  of  tin  foil  to  exclude  light     over  them.    Leave  in  a  bright  win- 

:ace-      dow,  or  preferably  out  of  doors,  for 

twenty-four  to  forty-eight  hours,  and  then  test  for  starch  as 

in  the  last  experiment ;  do  you  find  any  in  the  shaded  spots  ? 

Cover  the  lower  side  of  several  leaves  with  vaseline  or 
other  oily  substance  so  as  to  exclude  the  air,  and  after  a 
day  or  two  test  as  before. 

From  these  experiments  we  learn  that  leaves  can  not  do 
their  work  without  light  and  air.  The  particular  element 
of  the  atmosphere  used  by  them  in  the  process  of  food 
making  is  carbon  dioxide,  a  poisonous  gas  that  is  being 
constantly  produced  by  the  decay  of  vegetable  and  animal 
matter,  by  the  respiration  of  animals,  and  by  combustion  of 
all  sorts.  It  constitutes  about  one  fourth  of  one  per  cent 
of  our  atmosphere,  and  when  the  proportion  rises  much 
above  this,  the  air  becomes  unfit  to  breathe,  so  that  the 
work  of  plants  in  eliminating  it  is  a  very  important 
one. 

28.  Respiration.  — The  leaf  is  also  an  organ  of  respira- 
tion ;  that  is,  it  is  always  taking  in  oxygen  and  giving  off 
carbon  dioxide,  just  as  animals  do,  but  in  such  small  quan- 
tities that  the  process  is  entirely  obscured  during  the  day 
by  the  much  more  active  function  of  photosynthesis,  or 
food  making,  which  goes  on  at  the  same  time.  For  this 


RESPIRATION    AND    FOOD   PRODUCTION  25 

reason  it  was  formerly  believed  that  respiration,  or  the 
absorption  of  oxygen  by  plants,  took  place  only  at  night, 
and  some  people  were  led  to  imagine  from  this  that  it  is 
unwholesome  to  have  potted  plants  in  a  bedroom ;  but  the 
quantity  of  oxygen  absorbed  by  green  plants  is  so  small 
as  to  be  scarcely  appreciable. 

While  the  leaf  is  the  principal  organ  of  respiration,  this 
function  is  carried  on  in  other  parts  of  the  plant  also,  else 
it  could  not  survive  during  the  leafless  months  of  winter. 
It  goes  on  at  all  times,  in  all  living  parts,  and  the  other 
leaf  functions  also  are  carried  on,  to  some  extent,  in  all 
green  tissues. 

/ 

29.    Relation  of  Respiration  to  Other  Functions.  —  The 

functions  of  photosynthesis  and  respiration  are  mutually 
complementary  and  interdependent,  the  one  manufacturing 
food,  and  the  other  using  it  up,  or  rather  marking  the  activity 
of  those  life  processes  by  which  it  is  used  up.  In  this 
respect  it  is  strictly  analogous  to  the  respiration  of  animals. 
The  more  we  exert  ourselves  and  the  more  vital  force 
we  expend,  the  harder  we  breathe,  and  hence  respiration 
is  more  active  in  children  than  in  older  persons,  and 
in  working  people  than  in  those  at  rest.  It  is  just  the 
same  with  plants ;  respiration  is  always  most  energetic 
in  germinating  seedlings  and  young  leaves,  in  buds  and 
flowers,  where  active  work  is  going  on  ; 
hence  such  organs  consume  propor- 
tionately large  quantities  of  oxygen 
and  liberate  correspondingly  large 
quantities  of  carbon  dioxide. 

Fill  a  glass  jar  of  two  liters'  capacity 
(about  two  quarts)  with  germinating 
seeds,  or  with  flower  buds  or  unfolding 
leaf  buds  arranged  in  layers  alternating 
with  damp  cotton  batting  or  blotting 
paper;  close  it  tightly  and  leave  it  for  10.— Arrangement  of 
twelve  to  twenty-four  hours.  If  the  aPParatus.  to  show  that 

•*  carbon   dioxide   is  given 

jar  is  then  opened  and  alighted  taper    off  by  germinating  seeds. 


26  THE   LEAF 

plunged  in,  it  will  be  extinguished  as  quickly  as  in  the 
empty  tumbler  in  the  experiment  described  in  Section  23, 
thus  showing  that  the  process  of  respiration  is  more  active 
in  this  case  than  the  opposite  function  of  taking  in  carbon 
dioxide  and  liberating  oxygen.  Insert  a  thermometer  bulb 
and  note  the  difference  in  temperature.  In  some  of  the 
arums,  — calla  lily,  Jack-in-the-pulpit,  elephant's  ear  (Colo- 
casia),  etc.,  —  where  a  large  number  of  small  flowers  are 
brought  together  within  the  protecting  spathe,  the  rise 
of  temperature  is  sometimes  so  marked  that  it  may  be 
perceived  by  placing  a  flower  against  the  cheek.1 

30.  Metabolism.  —  The  total  of  all  the  life,  processes  of 
plants,  including  growth,  waste,  repair,  etc.,  is  summed 
up  by  botanists  under  the  general  term  Metabolism.  It  is 
a  constructive  or  building-up  process  when  it  results  in 
the  making  of  new  tissues  out  of  the  food  absorbed  from 
the  earth  and  air,  and  consequent  increase  of  the  plant 
in  size  or  numbers.  But,  as  in  the  case  of  animals,  so 
with  plants,  not  all  the  food  provided  is  converted  into 
new  tissue,  a  part  being  decomposed  and  excreted  as 
waste.  In  this  sense,  metabolism  is  said  to  be  destructive, 
and,  like  other  destructive  processes  (combustion,  for  in- 
stance), is  always  accompanied  by  the  liberation  of  energy,  — 
heat,  as  we  have  seen,  being  an  invariable  accompaniment. 
The  waste  in  healthy  plants  is  always,  of  course,  less  than 
the  gain,  and  a  large  portion  of  the  food  material  is  in 
all  cases  laid  by  as  a  reserve  store.  For  this  reason, 
photosynthesis,  which  is  a  constructive  process,  is  usually 
more  energetic  than  respiration,  which  is  the  measure  of 
the  destructive  change  of  materials  that  attends  all  life 
processes. 

It  is  evident  also,  from  what  has  been  said,  that  growth 
and  repair  of  tissues  can  take  place  only  so  long  as  the 
plant  has  abundant  oxygen  for  respiration,  since  the  food 
material  manufactured  by  it  must  be  decomposed  into  the 

1  See  Sachs,  "  Physiology  of  Plants." 


THE   TYPICAL   LEAF  AND   ITS   PARTS  27 

various  substances  required  by  the  different  tissues  before 
it  can  be  appropriated  by  them. 

PRACTICAL  QUESTIONS 

1.  Why  do  gardeners  bank  up  celery  to  bleach  it  ?    (25.) 

2.  Why  are  the  buds  that  sprout  on  potatoes  in  the  cellar  white?  (25.) 

3.  Why  does  young  cotton  look  so  pale  and  sickly  in  long-continued 
wet  or  cloudy  weather  ?     (25.) 

4.  Why  do  parasitic  plants  generally  have  either  no  leaves  or  very 
small,  scalelike  ones  ?     (25.) 

5.  The  mistletoe  is  an  exception  to  this  ;  can  you  tell  why  ?    (184.) 

6.  Could   an   ordinary   self-supporting   plant    live   without    green 
leaves  ?     (26,  27.) 

7.  Are  abundance  and  color  of  foliage  any  indication  of  the  health 
of  a  plant  ?     (24,  26.) 

8.  Is  the  practice  of  lopping  and  pruning  very  closely,  as  in  the 
process  called  "pollarding,"  beneficial  to  a  tree  under  ordinary  con- 
ditions ?     ( 1 8,  21,  24,  26.) 

9.  Why  is  it  wise  to  trim  a  tree  close  when  we  transplant  it  ? 
(20,  21.) 

10.  Why  should  transplanting  be  done  in  winter  or  very  early  spring, 
when  the  leaves  are  off  ?  ( [9,  20.) 

u.  Name  some  plants  of  your  neighborhood  that  grow  well  in  the 
shade. 

12.  Compare  in  this  respect  Bermuda  grass  and   Kentucky  blue 
grass ;    cotton   and   maize ;    horse   nettle   (Solanum   carolinense)    and 
dandelion  ;  beech,  oak,  red  maple,  dogwood,  pine,  cedar,  holly,  mag- 
nolia, etc. 

13.  Why  are  evergreens   more  abundant  in  cold  than  in   warm 
climates  ?     (19,  exp.) 

14.  Is  it  wholesome  to  keep  blooming  plants  in  a  bedroom  ?     Leafy 
ones  ? 

15.  Why,  in  each  case  ?     (23,  28.) 

THE  TYPICAL  LEAF  AND  ITS  PARTS 

MATERIAL.  —  Leaves  of  as  many  different  kinds  as  can  conveniently 
be  obtained,  showing  their  various  modes  of  attachment,  shapes,  tex- 
ture, etc.  For  stipules,  leaves  on  very  young  twigs  should  be  sought 
for,  as  these  bodies  often  fall  away  soon  after  the  leaves  expand.  The 
rose.  Japan  quince  {Pyrnsjaponica),  willow,  strawberry,  pansy,  pea,  and 
young  leaves  of  apple,  peach,  elm,  oak,  beech,  tulip  tree  {Liriodendroti), 
India  rubber  tree  (Ficus  elastica),  magnolia,  etc.,  furnish  good  exam- 
ples of  stipules. 


THE    LEAF 


31.  Parts  of  the  Leaf.  —  Examine  a  young,  healthy  leaf 
of  apple,  quince,  elm,  etc.,  as  it  stands  upon  the  stem,  and 
notice  that  it  consists  of  three  parts : 
a  broad  expansion  called  the  blade ;  a 
leaf  stalk  or  petiole  that  attaches  it  to 
the  stem;  and  two  little  leaflike  or 
bristlelike  bodies  at  the  base,  known 
as  stipules.  Make  a  sketch  of  any  leaf 
provided  with  all  these  parts  and  label 
them  respectively  blade,  petiole,  and 
stipules.  These  three 


ii. -A  typical  leaf  and   Pal"tS 
its  parts :  b,  blade ;  /,  peti-   Or   typical  leaf,  but   as  a 
ole ;  s,  s,  stipules. 

matter   of    fact,   one  or 
more  of  them  is  usually  wanting. 


32.    Stipules.  —  The    office    of    stipules, 

when  present,  is  generally  to  subserve 
in  some  way  the  pur- 
poses of  protection.  In 
many  cases,  as  the  fig, 
elm,  beech,  oak,  magno- 
lia, etc.,  they  appear  only  as  protective 
scales  that  cover  the  bud  during  winter, 
and  fall  away  as  soon  as  the  leaf  ex- 
pands. When  persistent,  that  is,  en- 
during, they  sometimes  take  the  form 
of  spines  and  thorns,  as  in  the  black 
locust  and  spiny  clotbur  (Xanthium 
spinosum}.  The  sheathing  stipules  of 

of  -"prince's  feather"  (Po-  the  smartwceds  and  bindweeds  (Polygo- 

lygonum  oriental,)  (GRAv).    ^^  ^^  ^  strengthen  ^  gtem  ^  ^ 

joints  (Fig.  13),  and  the  adnate  stipules  (Fig.  14)  of  the 
rose,  clover,  strawberry,  etc.,  may  serve  either  as  water 
holders  or  as  shields  against  climbing  insects.  In  the  smi- 
lax  and  some  other  vines  they  appear  as  tendrils  for  climb- 
ing, while  in  other  cases,  as  the  garden  pea  and  pansy,  they 
become  large  and  leaflike,  or  may  even  usurp  the  place  of 


THE   TYPICAL   LEAF   AND   ITS   PARTS  29 

the  leaves  altogether,  as  in  the  Lathyrus  aphaca  (Fig.  17), 


14.  —  Adnate  stipules  of 
clover. 


15.  —  Leaves  of  smilax,  show- 
ing stipular  tendrils. 


16.  —  Leafy  stipules  of 
Japan  quince. 


a  near  relative  of  the  sweet  pea,  where  they  function  as 

foliage.     But  under  whatever  form 

they  occur,   their   true  nature  may 

be  recognized  by  their  position  on 

each  side  of  the  base  of  the  petiole, 

and  not  in  the  axil,  or  angle  formed 

by  the  leaf  with  the  stem. 


17.  —  Leaf   of    LatAyrus 
aphaca,    reduced   to   a  pair 
nd    a    tendril 


33.  Petioles.  —  The  normal  use  of 
the  petiole  is  to  secure  a  better 
light  exposure  for  the  leaves,  but 
like  other  parts  of  the  leaf,  it  is 
subject  to  modifications.  In  some  vines,  such  as  the  jas- 
mine nightshade  and  tropaeolum  of  the  gardens,  it  is 
twisted  into  a  tendril  for  climbing.  Occasionally  the  leaf 
blade  disappears  altogether  and  the  leaf  stalk  takes  its 
place,  as  in  some  of  the  Australian  acacias  frequently  seen 
in  greenhouses.  Simulated  leaves  of  this  kind  can  gen- 
erally be  distinguished  by  their  edgewise  position,  the 
blades  of  true  leaves  being  usually  horizontal.  Other 
instances  occur,  such  as  the  onion,  jonquil,  hyacinth,  etc., 
where  the  distinction,  if  any  exists,  is  difficult  to  make  out. 


30  THE   LEAF 

In  the  sycamore,  the  base  of  the  petiole  is  hollowed  out 
into  a  socket  to  protect  the  bud  of  the  season  (Fig.  20). 

34.  Leaf  Attachment.  —  When  the  petiole  is  wanting 
altogether,  as  is  often  the  case,  leaves  are  said  to  be  sessile, 
that  is,  seated  on  the  stem,  and  their  bases  are  described 
by  various  terms  suggestive  of  the  mode  of  attachment. 
You  can  frame  your  own  definition  of  these  terms  by  an 
inspection  of  the  accompanying  figures,  or  better  still,  of 
some  of  the  sample  plants  named  in  connection  with 
each. 

Clasping  (Fig.  21):  Wild  lettuce  (Lactuca),  chicory,  sow 
thistle  (Sonchns\  poppy,  stem  leaves  of  turnip,  mustard,  etc. 

Decurrent  (Fig.  22) :  Thistle,  sneezeweed  (Helenium 
autumnale\  comfrey  (Symphytum). 

Connate  (Fig.  23):  The  upper  leaves  of  boneset  (Eupa- 
torium  perfoliatum)  and  trumpet  honeysuckle  (Lonicera 
semperuirens). 

Perfoliate  (Fig.  24) :  Bellwort  (Uvularia  perfoliata). 

Peltate,  or  shield-shaped  (Fig.  25):  Castor  oil  plant, 
trop^olum,  May  apple  (Podopkyllum),  water  pennywort 
(Hydrocotyle). 

Equitant  (Fig.  26) :  Iris,  sweet  flag  (Acorus  calamus}, 
blackberry  lily  (Belamcanda  chinensis). 

35.  The  Use  of  Botanical  Language.  —  These  terms  and 
those  which  follow  are  not  to  be  learned  by  heart,  but  are 
given  here  merely  for  convenience  of  reference.  Botanists 
have  invented  a  number  of  useful  terms  for  describing 
things  briefly  and  accurately,  and  while  they  are  not  to  be 
regarded  as  of  any  importance  in  themselves,  it  is  impos- 
sible to  get  along  without  some  knowledge  of  them  ;  for 
besides  furnishing  a  sort  of  universal  vocabulary,  intelli- 
gible to  botanists  everywhere,  they  enable  us  to  say  in  two 
or  three  words  what  it  would  otherwise  require  as  many 
lines  or  perhaps  paragraphs  to  express.  In  other  words, 
they  are  a  sort  of  labor-saving  device  which  every  botanist 
must  learn  how  to  use,  as  no  good  workman  can  afford  to 
be  ignorant  of  the  tools  of  his  profession. 


THE  TYPICAL  LEAF  AND  ITS  PARTS 


3-26.  —  Petioles,  and  leaf  attachment:  18,  petioles  of  jasmine  nightshade 
(Solatium  jasminoides)  acting  as  tendrils ;  19,  acacia,  showing  petiole  transformed 
to  leaf  blade ;  20,  petiole  of  sycamore  hollowed  out  to  protect  the  bud  of  the  season  ; 
21,  clasping  leaf  of  lactuca;  22,  decurrent  leaf  of  thistle;  23,  connate  leaves  of 
honeysuckle;  24,  perfoliate  leaves  of  uvularia ;  25,  peltate  leaf  of  tropseolum ; 
26,  equitant  leaves  of  iris.  (18,  20,  23.  24,  25,  and  26,  after  GRAY.) 


32  THE   LEAF 

36.  Shape  and  Texture  of  Leaves.  —  Examine  a  number 
of  leaves  of  different  kinds  and  see  how  they  differ  from 
each  other  in  regard  to  — 

General  Outline:  whether  round,  oval,  heart-shaped, 
lanceolate,  etc.  (Figs.  27-33). 


27-33.  — Shapes  of  leaves:    27,  lanceolate;   28,  spatulate;    29,  oval;    so.obovate; 
31,  reniform,  or  kidney-shaped;  32,  deltoid  ;  33,  lyrate.     (27-31,  after  GRAY.) 


Base:    tapering,   obtuse,   truncate,    cordate,   etc.  (Figs. 
34-38). 


34-38.— Bases  of  leaves:    34,  cordate;    35,  sagittate;    36,  oblique;    37,  auricled ; 
38,  hastate. 


39-47.  —  Apexes  of  leaves :    39,  acuminate;    40,  acute;   41.  obtuse;    42,  truncate; 
43,44,  emarginate;  45,  obcordate;  46,  cuspidate;  47,  mucronate  (GRAY). 


Apex :  acute,  acuminate,  emarginate,  etc.  (Figs.  39-47). 


THE  TYPICAL  LEAF  AND  ITS  PARTS 


33 


Margins :    some   being   unbroken   or 
entire,  others  variously  toothed  and  cut        /^ 
(Figs.  48-53> 


48~53-  —  Margins  of  leaves:   48,  serrate;  49,  dentate;  50,  crenate;  51,  undulate; 
52,  sinuate ;  53,  runcinate  leaf  of  dandelion!       (48-52,  after  GRAY.) 

Symmetry :  that  is,  whether  the  two  halves  are  alike,  so 
that  if  folded  over  on  each  other  they  would  coincide. 

Texture :  whether  thick  or  thin,  fleshy  and  soft,  hard 
and  brittle,  or  tough  and  leathery  (coriaceous). 

Surface :  smooth  and  shining  (glabrous) ;  wrinkled  (ru- 
gose) ;  hairy  (pubescent) ;  covered  with  a  bloom  (glaucous) ; 
moist  and  sticky  (viscid,  or  glandular). 


PRACTICAL  QUESTIONS 

1 .  Tell  the  nature  and  use  of  the  stipules  in  such  of  the  following 
plants  as  you  can  find  :  tulip  tree  ;  fig ;  beech  ;  apple ;  willow  ;  pansy ; 
garden  pea;  Japan  quince  (Pyrus  japonica)  •  sycamore;  rose;  paper 
mulberry  (Broussonetia). 

2.  State  what  differences  and  resemblances  you  observe  between  the 
leaves  of  the  elm,  beech,  birch,  alder,  hackberry,  hornbeam. 

Between  the  hickory,  ash,  common  elder,  walnut,  ash-leaved  maple 
{Negundo),  ailanthus,  sumac. 

Between  the  persimmon,  black  gum,  buckthorn,  papaw  (Asttttina), 
sourvvood  (Oxydendron  arboreuni). 

Between  chinquapin,  chestnut,  and  chestnut  oak. 

Any  other  sets  of  leaves  may  be  substituted  for  those  named,  the 
object  being  merely  to  form  the  habit  of  distinguishing  readily  the  dif- 
ferences and  resemblances  between  leaves  that  bear  some  general  like- 
ness to  one  another. 

Notice  that  the  general  resemblances  are  not  confined  to  plants  of 
closely  related  species :  what  other  causes  may  influence  them  ? 

ANDREWS'S    BOT.  —  3 


34 


THE   LEAF 


VEINING 


MATERIAL.  —  A  specimen  of  each  of  the  different  kinds  of  veining. 
For  parallel  veining  any  kind  of  arum,  lily,  or  grass  will  do  :  for  net 
veining,  ivy,  maple,  elm,  or  peach,  etc.  Classes  in  cities  can  use  leaves 
from  potted  plants  of  wandering  Jew  (Zebrina  pendula),  calla  lily,  and 
other  easily  cultivated  specimens,  or  blades  of  grass,  plantain,  and  vari- 
ous parallel  and  net  veined  weeds  can  be  picked  up  here  and  there, 
even  in  the  largest  cities.  Have  a  number  of  leaves  placed  with  their 
cut  ends  in  red  ink  from  three  to  six  hours  before  the  lesson  begins. 

37.  Parallel  and  Net  Veining.  —  Com- 
pare a  leaf  of  the  wandering  Jew,  garden 
lily,  or  any  kind  of  grass,  with  one  of  cot- 
ton, maple,  ivy,  etc.  Hold  each  up  to 
the  light,  and  note  carefully  the  veins  or 
little  threads  of  woody  substance  that 
run  through  it.  Make  a  drawing  of 
each  so  as  to  show  plainly  the  direction 
and  manner  of  veining.  Write  under 
the  first,  Parallel  veined,  and  under  the 
"4.— Parallel-veined  secon^,  Net  veined.  This  distinction  of 
leaf  of  lily  of  the  valley  leaves  into  parallel  and  net  veined  cor- 

(after  GRAY).  ,          .  , 

responds  with  another  important  differ- 
ence in  plants,  existing  in  the  seed,  and  is  used  by  botanists 
in  distinguishing  the  two  great 
classes  into  which  seed^bearing 
plants  are  divided. 

38.  Pinnate  and  Palmate  Vein- 
ing.  —  Next,  compare  a  leaf  of 
the  canna,  or  of  any  of  our 
common  garden  arums,  with  one 

Of    the    elm,    peach,    cherry,  etc.,     55.— Palmately  net-veined  leaf  of 

or  with  a  leaflet  of  the  rose  or  ******#***. 

clover.  Hold  both  up  to  the  light  and  observe  carefully 
the  veins  and  reticulations.  What  resemblance  do  you 
notice  between  the  two?  What  difference?  Which  is 
parallel  veined  and  which  is  net  veined  ?  Make  a  drawing 
of  each,  and  compare  with  the  first  two.  Notice  that 


VEINING 


35 


56.  —  Pinnately  paral- 
lel-veined leaf  of  calla  lily 


57-  —  Pinnately  net- 
veined  leaf  of  awillow. 


in  the  last,  the  petiole  seems  to  be  continued  in  a  large 
central  vein,  called  the  Midrib,  from 
which  the  secondary  veins  branch  off 

on    either    side    just 

as    the   pinnae    of    a 

feather  do  from  the 

quill ;    whence     such 

leaves  are  said  to  be 

pinnately,    or  feather 

veined.      In  the  cot- 
ton, maple,  ivy,  etc., 

on    the    other    hand, 

the  petiole  breaks  Up 

at  ^  base  of  the  leaf  (Fig.  55)  into  a 
number  of  primary  veins  or  ribs,  which  radiate  in  all  direc- 
tions like  the  fingers  from  the  palm  of  the  hand ;  hence, 
such  a  leaf  is  said  to  be  palmately  veined* 

39.  Ribbed  Leaves.  —  Net-veined  leaves  are  sometimes 
ribbed  in  a  way  that  might  lead  an  inexperienced  observer 
to    confound    them    with     parallel-veined 

ones.  Compare,  for  instance,  a  leaf  of 
the  wild  smilax  (often  improperly  called 
bamboo),  or  of  the  common  plantain,  with 
one  of  the  kind  represented  in  Figure  54. 
A  little  inspection  will  show  that  in  both 
the  ribs  all  proceed  from  the  same  point 
at  the  top  of  the  petiole,  as  in  other 
leaves  of  the  palmate  kind,  of  which  they 
are  varieties,  but  the  reticulations  between 
the  ribs  in  the  smilax  and  plantain  show 
that  they  belong  to  the  net-veined  division. 

40.  Parallel- veined    and    Straight-veined    Leaves.  —  In 
some  pinnate  leaves,  like  the  elm,  beech,  birch,  dogwood, 
etc.,  the  secondary  veins  are  so  straight  and  regular  that 
beginners  are  apt  to  confound  them  with  the  parallel  kind 
represented  in  Figure  56,  but  this  mistake  need  never  occur 


35  THE   LEAF 

if   the  reticulations   of    the   smaller  veinlets    are   noted. 

Then,  too,  it  must  be  observed  that  in  a  pinnately  parallel- 
veined  leaf  the  secondary  veins  do 
not  separate  from  the  midrib  in  such 
sharp,  clear-cut  angles  as  we  see  in  the 
beech  and  elm,  but  seem  to  flow  into 

59.  —  straight-veined  leaf  jt  an(j  mingle  gradually  with  it,  so  that 
the  midrib  has  the  appearance  of 

being  made  up  of  the  overlapping  fibers  of  the  smaller 

veins,  as  in  Figure  56. 

41.  Use  of  the  Veins.  —  Hold  up  a  stiff,  firm  leaf  of  any 
kind,  like  the  magnolia,  holly,  or  India  rubber,  to  the  light, 
having  first  scraped  away  a  little  of  the  under  surface,  and 
examine  it  with  a  lens.     Compare  it  with  one  of  softer  tex- 
ture, like  the  peach,  maple,  grape,  cotton,  clover,  etc.     In 
which  are  the  veins  closest  and  strongest  ?     Which  is  most 
easily  torn  and  wilted  ?     Tear  a  blade  of  grass  longitudi- 
nally and  then  crosswise ;  in  which  direction  does  it  give 
way  most  readily  ?     Tear  apart  gently  a  leaf  of  cotton, 
maple,  or  ivy,  and  one  of  elm  or  other  pinnately  veined 
plant ;    in  which  direction  does  each  give  way  with  least 
resistance  ?     What  would  you  judge  from  these  facts  as  to 
the  office  of  the  veins  ? 

42.  Effect  upon  Shape.  —  By  comparing   a   number  of 
leaves  of  each  kind,  it  will  be  seen  that  the  feather-veined 
ones  tend  to  assume  elongated  outlines  (Figs.  16,  33,  53), 
while  the  palmate  veining  produces  more  broad  and  rounded 
forms  (Figs.  25,  55,  61).      Notice  also  that  the  straight, 
unbroken  venation  of  parallel-veined  leaves  is  generally 
accompanied    by   smooth,    unbroken    margins,    while    the 
irregular,  open  meshes  of  net-veined  leaves  are  favorable 
to  breaks  and  indentations  of  all  kinds. 

43.  Veins  as  Water  Pipes. —Examine  a  leaf   that   has 
stood  in  red  ink  for  two  or  three  hours.     Do  you  see  evi- 
dence that  it  has  absorbed  any  of  the  liquid  ?     Cut  across 
the  blade  and  examine  with  a  lens.     What  course  has  the 


BRANCHED   LEAVES  37 

absorbed  liquid  followed  ?  What  use  does  this  indicate  for 
the  veins,  besides  the  one  already  noted  ? 

We  thus  see  that  the  veining  serves  two  important  pur- 
poses in  the  economy  of  the  leaf ;  first,  as  a  skeleton,  or 
framework,  to  support  the  expanded  blade ;  and  second,  as 
a  system  of  supply  pipes,  or  waterworks  for  conveying 
the  sa.p  out  of  which  its  food  is  manufactured. 

The  microscope  shows  us  that  the  veins  are  made  up  of 
clusters  or  bundles  of  woody  fibers,  mixed  with  long,  tubu- 
lar cells  that  serve  as  vessels  for  conducting  the  sap;  hence 
they  are  called  fibrovascular  bundles ;  which  means  bun- 
dles composed  of  fibers  and  conducting  vessels.  In  this 
way  the  veins  get  both  their  hardness  and  their  water- 
conducting  power.  The  tough,  stringy  threads  that  pro- 
trude from  the  petiole  of  a  plaintain  leaf  when  broken  are 
made  of  fibrovascular  bundles  that  supply  the  leaf  blade. 

PRACTICAL  QUESTIONS 

1.  In   selecting  leaves   for  decorations  that  are  to  remain  several 
hours  without  water,  which  should   you  prefer,  and  why :   Smilax  or 
Madeira  vine  (Boussingaultia)!     Ivy  or  Virginia  creeper?     Magnolia 
or  maple?     Maidenhair  or  shield  fern  {Aspidiuni)!    (41,43.) 

2.  Should  you  select  very  young  leaves,  or  more  mat  are  ones,  and 
why? 

3.  Can  you  name  any  parallel-veined  leaves  that  have  their  margins 
lobed,  or  indented  in  any  way? 

4.  Which  are  most  common,  parallel-veined  or  net-veined  leaves? 

5.  Why  do  the  leaves  of  corn  and  other  grains  not  shrivel  length- 
wise in  withering,  but  roll  inward  from  side  to  side?    (41.) 

6.  Can  you  name  any  pahnately-veined  leaves  in  which  the  secondary 
veins  are  pinnate?     Any  pinnately-veined  ones  in  which  the  secondary 
veins  are  palmate? 

7.  Account  for  the  difference. 

BRANCHED   LEAVES 

MATERIAL.  —  Lobed  and  compound  leaves  of  various  kinds.  Many 
good  examples  can  be  found  among  the  weeds  growing  on  vacant  lots 
in  cities. 

44.  Lobing.  —  Compare  the  outline  of  a  leaf  of  maple 
or  sweet  gum  with  one  of  oak  or  chrysanthemum.  Do 


THE   LEAF 


you  perceive  any  correspondence  between  the  manner  of 
lobing  or  indentation  of  their  margins,  and  the  direction 
of  the  veins  ?     To  what  class  would  you  refer  each  one  ? 
The  lobes  themselves  may  be  variously  cut,  as  in  the 


60.  —  Pinnately  lobed  leaf  of  an  oak. 


61.  —  Palmately  lobed  leaf  of  grape. 


fennel  and  rose  geranium,  thus  giving  rise  to  twice-cleft, 
thrice-cleft,  four-cleft,  or  even  still  more  intricately  divided 
leaves.  Where  the  divisions  are  very  deep  it  may  some- 
times be  a  little  puzzling  to  decide  whether  they  are  not 


62. —  Pinnately  divided  leaf 
of  a  buttercup. 


63.  —  Palmately  parted  leaf  of  tall  butter- 
cups. 


separate  leaflets,  but  if  there  is  the  merest  thread  of  green 
connecting  the  segments,  as  in  Figures  62  and  63,  it  is  con- 
sidered a  simple  lobed  leaf. 

45.    Compound  Leaves.  —  Compare  with    the  specimens 
just  examined  a  leaf  of  horse-chestnut,  clover,  or  Virginia 


BRANCHED   LEAVES 


39 


creeper,  etc.,  and  one  of  rose,  black  locust,  vetch,  or  other 
pinnate   leaf.      Notice   that   each   of 
<^^~>  these    last    is    made    up    of    entirely 

separate    divisions    or    leaflets,    thus 


64. —  Pinnately  compound 
leaf  of  black  locust. 


65.  —  Palmately  compound  leaf  of  horse- 
chestnut. 


forming  a  compound  leaf.  Notice  also  that  the  two  kinds 
of  compound  leaves  correspond  to  the  two  kinds  of  vein- 
ing  and  lobing,  so  that  we  have  palmately  and  pinnately 
compound  ones.  In  pinnate  leaves  the  continuation  of 
the  common  petiole  along  which  the  leaflets  are  ranged 
is  called  the  Rhachis. 

46.  Trifoliolate  Leaves.  —  In  a  trifoliolate  leaf,  or  one 
of  three  parts,  it  is  often  difficult  for  a  beginner  to  decide 
whether  the  divisions  are  palmate  or  pinnate.  To  settle 
this  question,  compare  a  leaf  of  lucerne,  beggar's  ticks,  or 


66.  —  Pinnately  trifoliolate  leaf  of  a 
desmodium. 


67. —  Palmately  trifoliolate  leaf  of 
wood  sorrel. 


bush  clover  (Lespedeza),  with  one  of  wood  sorrel  (Oxalis), 
or  any  common  clover,  and  observe  the  mode  of  attach- 
ment of  the  terminal  leaflet.  When  the  common  petiole 
is  prolonged  ever  so  little  beyond  the  insertion  of  the 


THE    LEAF 


two  lateral  leaflets,  so  as  to  form  a  rhachis,  as  in  Figure  66, 
the  leaf  is  pinnately  trifoliolate ;  but 
if  all  three  appear  to  spring  directly 
from  the  top  of  the  petiole,  as  in 
Figure  67,  it  is  palmate..  A  good  exam- 
ple of  a  pinnately  trifoliolate  leaf,  and 
one  which  it  is  important  to  learn  and 
remember,  is  the  poison  ivy. 

47.  Unity  of  Plan  in  Nature. — 
Notice  how  the  same  plan  of  structure 
runs  unchanged  through  all  these 
.—poison  ivy.  variations.  If  an  oak  or  a  tansy  leaf 
were  cut  through  to  the  midrib,  we  should  have  a  pinnately 
compound  leaf,  while  a  sweet  gum  or  a  maple  cut  in  the 
same  way  would  give  rise  to  a  palmately  compound  one. 

48.  The  Branching  of  Leaves.  —  Lobed  and  compound 
leaves  represent  mere  degrees  of  branching.     Notice,  how- 
ever, that  their  mode  of  branching  differs  from  that  of 
stems  in  having  the  branches  all  in  the  same  plane,  like 
figures  cut  out  of  a  single  sheet  of  paper.     This  is  what 
we  should  expect  in  the  case  of  expanded  bodies  whose 
primary  object  is  exposure  to  the  light. 

49.  What  makes  a  Compound  Leaf.  —  Some  botanists  do 
not  regard  a  branched  leaf  as  compound  unless  the  leaflet* 
are  jointed  to  the  common  petiole  so  that  they  break  and 
fall   away  separately  in   autumn,   like  those  of   the   ash, 
horse-chestnut,  china  tree,  etc.      According   to  this  defi- 


69.  —  Leaf  of  common  orange. 


7°-  —  Leaf  of  trifoliolate  orange. 


PHYLLOTAXY,   OR    LEAF   ARRANGEMENT  41 

nition,  the  single  leaf  of  the  orange  and  lemon  is  compound, 
for  it  is  jointed  to  the  petiole  like  those  of  the  ash  and 
hickory.  This  view  is  supported  by  the  fact  that  some 
species  of  orange  have  trifoliolate  leaves. 

PRACTICAL  QUESTIONS 

1.  State  whether  such  of  the  following  leaves  as  you  can  find  are 
lobed  or  compound :  cinquefoil,  wood  anemone,  tree  fern  {Polypodium 
incanu/fi),    buttercups,    Dutchman's    breeches    {Dicentrd),    mayweed, 
chamomile,  yarrow,  tickseed  (coreopsis},  shield  fern,  agrimony,  tomato, 
tansy,  cosmos,  cypress  vine,  wild  carrot,  larkspur,  strawberry,  monks- 
hood,  celandine. 

2.  Which    of  the    following   are    pinnately   and   which    palmately 
trifoliolate?      Lucerne,  red  clover,  Japan  clover  (Lespedeza  striata), 
beggar's  ticks   (Desmodiuvi),  sweet  clover  {Melilotus},  kidney  bean, 
strawberry. 

3.  Name  some  of  the  favorite  shade  trees  of  your  neighborhood ; 
do  they,  as  a  general  thing,  have  their  leaves  entire,  or  branched  and 
compound  ? 

4.  Which  of  the  following  are  the  better  shade  trees,  and  why :  pine, 
white   oak,   mimosa  (Albiazia\  sycamore,  locust,    horse-chestnut,  fir. 
maple,  linden,  China  tree,  cedar,  ash?. 

5.  Which  would  shade  your  porch  better,  and  why:  cypress  vine, 
grape,  gourd,  morning-glory,  wistaria,  clematis,  smilax,  kidney  bean, 
Madeira  vine,  rose,  yellow  jasmine,  passion  flower? 


PHYLLOTAXY,   OR  LEAF  ARRANGEMENT 


MATERIAL.  —  Twigs  of  any  kinds  of  plants  with  opposite  and  alter- 
nate leaves.  For  the  different  orders  of  alternate  arrangement,  elm, 
ivy,  basswood,  wandering  Jew,  or  any  kind  of  grass  will  show  the  first ; 
alder,  birch,  or  any  kind  of  sedge,  the  second ;  peach,  oak,  cherry,  or 
almost  any  of  our  common  trees  and  shrubs,  the  third  (in  cities,  a 
potato  plant  grown  in  a  pot  may  be  used).  In  selecting  specimens, 
choose  straight,  young  twigs  in  order  to  avoid  confusion  from  twisting 
of  the  stem  that  often  occurs  in  older  specimens  on  account  of  light 
exposure,  or  from  other  causes. 

50.  Alternate  and  Opposite  Leaves. — Compare  the  ar- 
rangement of  leaves  on  a  twig  of  elm  or  basswood,  or  on 
a  culm  of  grass,  etc.,  with  that  of  the  foliage  of  the  maple, 
lilac,  or  honeysuckle.  Make  a  vertical  diagram  of  each,  as 


42 


THE   LEAF 


shown  in  Figures  73  and  74,  illustrating  the  two  modes  of 
arrangement.     Label   the  point  at  which  the  leaf  is  in- 


7i  72  73  74 

71-74.  —  Arrangement  of  leaves:     71,   opposite-leaved  twig  of  spindle  tree; 
72,  alternate-leaved  twig  of  apple;   73,  vertical  diagram  of  opposite-leaved  twig; 

74,  vertical  diagram  of  two-ranked  twig  of  elm.     (71,  72,  after  GRAY.)  ' 

serted,  the  node ;  the  space  between  any  leaf  and  the  one 
next  above  or  below  it,  the  internode ;  and  angle  between 
the  leaf  and  the  stem,  where  you 
see  the  bud,  the  axil.  How  many 
leaves  are  there  at  a  node  in  the 
elm  and  basswood  ?  How  many  in 
the  maple  and  honeysuckle?  Are 
the  two  consecutive  pairs  of  leaves 
in  the  latter  placed  directly  over 
each  other,  or  at  right  angles  ?  How 

75.  — Horizontal  diagram  of    far  round  from  the  first  leaf  does 


opposite  leaves. 


the  second  stand  in  the  elm,  grass, 


etc.  ?  How  does  its  position  differ 
from  that  of  the  same  leaf  in  the 
opposite  mode  of  insertion  ?  How 
many  leaves  must  be  passed  in  order 
to  complete  a  turn  round  the  stem,  and 
what  leaf  in  numerical  order  stands 
directly  above  the  first  ?  Draw  a  hori- 

,      ,.  •  76. —  Horizontal  diagram 

zontal   diagram   of   both   twigs  repre-       of  two-ranked  leaves. 


PHYLLOTAXY,   OR   LEAF   ARRANGEMENT 


43 


senting  the  two  kinds  of  arrangement  as  viewed  from 
above.  Notice  that  if  we  join  the  leaves  in  the  opposite 
arrangement  by  dotted  lines  we  shall  get  a  series  of  circles 
(Fig.  75),  while  the  alternate  arrangement  will  give  a  spiral 
(Fig.  76). 

These  two  kinds  of  insertion,  the  alternate  and  opposite, 
represent  the  fundamental  forms  of  leaf  disposition.  There 
may  be  varieties  of  each,  but  no  matter  what  minor  differ- 
ences exist,  all  may  be  referred  to  one  of  these 
two  modes. 

51.  Whorled  and  Fascicled 
Leaves.  —  Where  more  than 
two  leaves  occur  at  a  node 
they  constitute  a  whorl,  or  ver- 
ticel,  as  in  the  trillium  and 
common  cleavers  (Gallium}. 
There  is  no  limit  to  the  num- 
ber of  leaves  that  may  be  in  a 
whorl  except  the  space  around 
the  stem  to  accommodate  them. 
A  'fascicle,  or  cluster,  of 
which  the  pine  and 
larch  furnish  exam- 
ples, is  composed  of  alternate  leaves  with  very 
short  internodes,  which  bring  the  leaves  so  close 
together  as  to  give  them  the 
appearance  of  a  whorl. 

52.  Varieties  of  Alternate 
Arrangement.  —  The  kind  of 
alternate  arrangement  just 
described  is  called  the  two- 
ranked,  because  it  distributes 
the  leaves  in  two  rows  on 
opposite  sides  of  the  stem ; 
in  other  words,  each  is  just  halfway  round  from  the  one 
next  above  or  below  it.  Other  common  forms  of  the  alter- 


77  78 

77-78.  —  Whorls  and  fascicles :  77, 
whorled  leaves  of  Indian  cucumber; 
78,  fascicled  leaves  of  pine. 


79~8o.  —  Three-ranked  arrange 
ment:  79,  vertical  diagram;  80,  hori 
zontal  diagram. 


44 


THE   LEAF 


81-82.—  Five-ranked  arrangement : 
8 1,  vertical  diagram;  82,  horizontal 
diagram. 


nate  or  spiral  arrangement  are  the  three-ranked  (Figs.  79 
and  80),  in  which  three  leaves  are  passed  in  completing  a 
turn  round  the  stem,  the  fourth  in  vertical  order 
standing  over  the  first;  and  the  five-ranked 
(Figs.  8 1  and  82),  in  which  five  leaves  are  passed 
in  making  two  turns,  and  the  sixth  in  numerical 
order  stands  above  the  first.  This  is  the  com- 
monest of  all  the  modes  of  insertion,  and  the 
one  that  prevails  among  our 
forest  trees  and  shrubs.  The 
two-ranked  is  characteristic 
of  the  grass  family,  and  the 
three-ranked  of  the  sedges, 
though  both  occur  among 
other  plants  as  well.  Speci- 
mens of  all  the  kinds  men- 
tioned should  be  examined 
and  compared  with  the  dia- 
grams. There  are  other  and  more  complicated  arrange- 
ments, but  they  are  not  common  enough  to  demand 
attention  here. 

53.  Relation  between  Phyllo- 
taxy  and  the  Shape  of  Leaves. 
—  Compare  the  vertical  distance 
between  leaves  on  the  same  and 
on  different  twigs ;  are  the  inter- 
nodes  all  of  the  same  length  ? 
Where  the  internodes  are  short, 
the  leaves  will  be  crowded  to- 
gether in  closer  vertical  rows. 

A  Compact  arrangement  Of  this  83.  — Narrow  leaves  in  crowded 
Sort  tends  tO  shut  off  light  from  vertical  rows. 

the  lower  leaves ;  hence,  in  plants  where  it  prevails,  the 
leaves  are  apt  to  be  long  and  narrow  in  proportion  to 
the  frequency  of  the  vertical  rows.  The  yucca,  oleander, 
Canada  fleabane,  and  bitterweed  (Helenium  tenuifolium\ 

all  illustrate  this  law. 


PHYLLOTAXY,   OR   LEAF   ARRANGEMENT 


45 


On  the  other  hand,  where  the  intercedes  are  long  or  the 
vertical  rows  few,  the  leaves  tend  to  assume  more  broad 
and  rounded  shapes,  as  in  the  cotton,  hollyhock,  sunflower, 
etc.  If  the  blades  are  much  cut  and  lobed,  so  that  the 


84.  —  Long  internodes  and  large 
leaves. 


85.  —  Dissected  leaves  overlapping 
one  another  without  injurious  shad- 
ing. 


sun  easily  strikes  through,  they  can  bunch  themselves  in 
almost  any  way  without  injurious  shading.  The  length  of 
the  internodes  depends,  to  a  large  extent,  upon  the  rapid- 
ity of  growth,  being  usually  much  greater  in  vigorous 
young  shoots  and  the  terminal  portion  of  the  main  stem 
than  in  the  lateral  branches. 


PRACTICAL  QUESTIONS 

1.  Strip  the  leaves  from  a  twig  of  one  order  of  arrangement  and 
replace  them  with  foliage  from  a  twig  of  a  different  order ;  for  instance, 
place  basswood  upon  white  oak,  birch  upon  lilac,  elm  upon  pear,  honey- 
suckle on  barberry,  etc.     Is  the  same  amount  of  surface  exposed  as  in 
the  natural  order? 

2.  What   disadvantage   would   it  be  to  a  plant  if  the  leaves  were 
arranged  so  that  they  stood  directly  over  one  another?     (24,  25,  27.) 

3.  Why  are  the  internodes  of  vigorous  young  shoots,  or  scions,  gen- 
erally so  long?     (53.) 

4.  If  the  upward  growth  of  a  stem  or  branch  is  stopped  by  pruning, 
what  effect  is  produced  upon  the  parts  below,  and  why? 

5.  Why  does  corn  grow  so  small  and  stunted  when  sown  broadcast 
for  forage  ? 

6.  What  is  the  use  of  " chopping'1  cotton? 


THE   LEAF 


LEAF  ADJUSTMENT 

MATERIAL.  — Upright  and  horizontal  twigs  from  the  same  plant,  any 
kind  obtainable.  A  potted  plant  of  oxalis,  spotted  medick,  white  clover 
or  Japan  clover  (Lespedeza  striata),  or  any  other  irritable  kind. 

54.  Leaves  adjust  themselves  to  Light.  —  Take  two 
sprigs,  one  upright,  the  other  horizontal,  from  any  con- 
venient shrub  or  tree  —  those  with  opposite,  or  two-ranked 
leaves,  like  the  elm  and  linden  will  generally  show  this 
peculiarity  best  —  and  notice  the  difference  in  the  position 
of  the  leaves.  Examine  their  points  of  attachment  and  see 
how  this  is  brought  about,  whether  by  a  twist  of  the  petiole 
or  of  the  base  of  the  leaf  blades,  or  by  a  half  twist  of  the 
stem  between  two  consecutive  leaves,  or  by  some  other 


86,  87.  —  Adjustment  of  leaves  to  different  positions :    86,  upright ; 
87,  procumbent. 

means.  Observe  both  branches  in  their  natural  position  ; 
what  part  of  the  leaf  is  turned  upward,  the  edge  or  the 
surface  of  the  blade?  Change  the  position  of  the  two 
sprigs,  placing  the  vertically  growing  one  horizontal,  and 
the  horizontal  one  vertical.  What  part  of  the  leaves  is 
turned  upward  in  each  ?  One  need  only  glance  at  the 
sky  on  any  bright  day  and  see  how  the  light  falls  to 
understand  the  meaning  of  this  adjustment.  Would  the 
same  amount  of  light  and  air  be  secured  by  any  other  ? 

Rose  bushes  and  a  few  other  plants  sometimes  take  on 
a  second  growth  in  late  summer  and  autumn.  If  you  can 
find  such  a  plant,  bend  a  young  vertical  branch  into  a  hori- 
zontal position,  and  a  horizontal  one  into  an  upright  position 
and  fasten  them  there.  Examine  at  intervals  and  note  the 
adjustment  of  the  new  leaves  as  they  develop. 


LEAF   ADJUSTMENT 


47 


55.    Mosaics   and   Rosettes.  —  A  very  little   observation 

will  show  that  trees  with  horizontal 

or  drooping  branches,  like  the  elm 

and  beech,  and  vines  growing  along 

walls    or   trailing    on   the    ground, 

generally   display   their   foliage   in 

fiat,    spreading    layers,    each    leaf 

fitting    in   between    the    interstices 

of  the  others  like  the  stones  in  a 

mosaic,  whence  this  has  been  called 

the  mosaic  arrangement.     In  plants 

of  more  upright  or  bunchy  habit,  on 

the  other  hand,  the  leaves  grow  at 

all  angles,  with  a  general  tendency  to  cluster  in  rosettes  at 

the  end  of  the  branches, 
as  in  the  magnolia,  horse- 
chestnut,  sweet  gum,  etc., 
thus  giving  rise  to  what 
is  known  as  the  rosette 
arrangement. 


.  —  Leaf  mosaic  of  elm. 


89  90 

89,90.  —  Horse-chestnut  leaves:  89,  leaf  rosette  seen  from  above;  90,  the  same 
seen  sidewise,  showing  the  formation  of  rosettes  by  the  lengthening  of  the  lower 
petioles. 

56.  Leaf  Cones  and  Pyramids.  —  These  forms  usually 
result  from  a  lengthening  of  the  lower  petioles  to  secure  a 
better  light  exposure  for  the  under  leaves,  or  from  an 
increase  in  the  size  of  the  leaves  themselves,  as  we  see  in 
the  rosettes  that  form  about  the  roots  of  our  common 
biennial  and  perennial  herbs  in  winter.  To  the  same 


THE    LEAF 


cause  is  due  the  pyramidal  shape  assumed  by  plants  like 
the  mullein  and  burdock,  with  large,  undi- 
vided leaves  which  the  light  cannot  strike 
through.  The  foliage  on  the  upright  stalk 
that  rises  from  these  rosettes  in  spring  con- 
stantly diminishes  from  the  ground  upward, 
giving  the  plant  the  general  outline  of  a 
sort  of  vegetable  Eiffel 
tower.  The  upper 
leaves,  too,  will  gener- 
ally be  found  to  assume 
a  more  or  less  vertical 
position  so  as  not  to  cut 

91.  -Leaf  pyramid    ^ff   too   much    light  from 
of  mullein.  those   below. 


lignt. 


57.  Heliotropism.-If  there  is   any 

doubt  about  the  object  of  all  these  open  window,  showing 
careful  adjustments  it  can  be  settled 
by  placing  any  healthy  young  potted 
plant  near  a  sunny  window  and  at  the  end  of  a  day  or  two, 
observing  the  position  of  the  leaves.  Then  turn  the  pot 
round  so  that  the  leaves  will  face  away  from  the  light, 
and  again,  after  a  few  days,  observe  any  change  that  has 
taken  place  in  their  position.  Try  the  experiment  as  often 
as  you  like  and  with  any  number  of  different  plants,  the 
result  will  be  the  same.  This  movement  of  plants  in 


93-  —  Rhubarb  plant  with  leaves  adjusted 
for  centripetal  drainage. 


94.  —  A  caladium  showing  centrif- 
ugal drainage. 


LEAF   ADJUSTMENT  49 

response  to  the  influence  of  light  is  called  heliotropism, 
a  word  that  means  "  turning  to  or  with  the  sun." 

58.  Leaf   Drainage.  —  Another    important    adjustment 
that  leaves   undergo   is   in   regard  to  water.     Notice  the 
leaves  of   tulips,  hyacinths,  beets, 

turnips,  and  of  bulbs  and  plants 
generally  whose  roots  do  not  spread 
in  a  horizontal  direction,  and  it 
will  be  found  that  their  leaves  usu- 
ally assume  a  position  more  or  less 
like  that  shown  in  Figure  93. 
Their  edges  are  apt  to  curve  in- 
wards and  they  slope  from  base 
to  apex  at  such  an  angle  as  to 
carry  most  of  the  water  that  falls 
upon  them  straight  to  the  axis  of  '  9S._Leaf  with  tapering 
growth,  and  so  on  down  to  the  P°int  that  acts  as  a  sutter  in 

conducting  off  water. 

root.      In  most  trees  and   shrubs, 

on  the  other  hand,  and  in  plants  generally  with  spreading 
roots,  the  leaves  slope  from  base  to  tip  so  that  the  water 
is  carried  away  from  the  axis  to  the  circumference,  where 
the  delicate  young  root  fibers  grow  that  are  most  active 
in  the  work  of  absorption.  In  the  first  case  the  drain- 
age is  said  to  be  centripetal,  or  towards  the  center  of 
growth ;  in  the  second,  it  is  centrifugal,  or  away  from  the 
center. 

59.  Leaf  Cups. —  The  water  could  not  well  run  down  a 
long,  slender  leaf  stalk  from  the  blade  to  the  stem,  hence, 
in  plants  fitted  for  centripetal  drainage  the  leaves  are  gen- 
erally sessile,  or  the  petioles  are  grooved  or  appendaged  in 
various  ways,  as  in  the  winged  leaf  stalks  of  the  sweet  pea 
and   the   common  leaf  cup   (Polyinnia),  which   takes  its 
name  from  the  cuplike  expansion  into  which  the  base  of 
the   petiole   is    often    dilated.     Connate   leaves   may  also 
serve  the  same  purpose.      Can  you   think  of  any  other 
probable  use  for  these  natural  water  holders  ?    Why.  for 

ANDREWS'S  EOT.  —  4 


THE   LEAF 


96.  —  Winged  petiole  of 
Polymnia. 


97.  —  Water  cups  of  Silphiur 
perfoliatum. 


instance,  do  housewives  sometimes  set   the  feet  of   their 
cupboards  in  vessels  of  water  ? 

60.   Protection  against  Excessive  Light  and  Heat.  —  With 
plants  growing  in  very  hot,  dry  climates,  or   in    exposed 
situations,  it  is  often  necessary  to  guard  against  too  rapid 
transpiration    by    shutting    off    the 
direct  rays  of  the  sun  from  the  sto- 
mata,  just  as  we  close  our  blinds  in 
summer  to  keep  the  heat  out.     The 
common    blackberry     lily    {Be  lam 
canda)  of  our  old  red  hillsides,  and 
98.—  Cross  sections  of  the    others  of  the  iris  family,  to  which 


c.  roiled  up  to  prevent  too    vertically  so  as  to  expose  only  the 

rapid  transpiration.  dps  ^Q  ^  full  ^^  Qf   ^  nOQnday 

sun.  Many  swamp  herbs  like  the  sweet  flag  (Acorns 
calamus],  the  cat-tails,  and  yellow-eyed  grass  (Xyris)  have 
the  same  habit,  the  pools  and  marshes  in  which  they  grow 
often  becoming  dry  in  summer  ;  and  moreover,  even  though 
there  may  be  plenty  of  moisture,  they  are  very  dependent 
upon  it  and  need  to  retain  a  good  store.  Strongly  revo- 
lute  margins,  such  as  are  found  in  many  sand  plants 
growing  along  the  seashore,  produce  the  same  effect  by 
inclosing  the  stomata  in  the  hollow  trough  or  cylinder 
formed  by  their  recurved  edges. 


LEAF   ADJUSTMENT 


61.  Compass  Plants.  —  A  very  remarkable  adjustment 
is  that  of  the  rosinweed,  or  com- 
pass plant  {Silphium  laciniatum\ 
which  grows  in  the  prairies  of  Ala- 
bama and  westward,  where  it  is 
exposed  to  intense  sunlight.  The 
leaves  not  only  stand  vertical,  but 
have  a  tendency  to  turn  their  edges 
north  and  south  so  that  the  blades 
are  exposed  only  to  the  gentler 
morning  and  evening  rays.  The 
prickly  lettuce  manifests  the  same 
habit. 


62.   Leaves   that  go   to   Sleep. — 

The  leaves  of  many  plants  change 


99  ioo 

99,  ioo. — A  compass  plant, 
rosinweed    (Silphium    lacini- 
atunt):     99,    seen    from    the 
their  position    at   night   as  if    folding     east  ;     100,    seen    from    the 

themselves  for  sleep.     This  habit  is    south' 
especially  noticeable  in  certain  members  of  the  pea  family 
and  also  in  the  wood  sorrel  and  the  cultivated  oxalis  of 
the  gardens.     The  motions  may  be  either  spontaneous,  as 
in  the  telegraph  plant  (Desmodinm  gyrans),  or  in  response 

to  various  external 
agents,  as  light,  heat, 
irritation  by  contact 
with  other  sub- 
stances, etc.  The  po- 
sitions assumed  are 
various  and  may 
even  differ  in  differ- 
ent parts  of  the  same 
compound  leaf ;  in 
the  kidney  bean  {Phaseolus),  for  instance,  the  common 
petiole  turns  up  at  night  and  the  separate  leaflets  down. 

63.  Experiments.  —  Place  a  healthy  plant  of  oxalis, 
spotted  medick,  or  white  clover  in  a  pot  and  keep  it  in  your 
room  for  observation.  Notice  the  changes  of  position  the 
leaves  undergo.  Sketch  one  as  it  appears  at  night  and  in 


101,  102.  — Spotted  medick:    101,  awake; 
102,  asleep. 


52  THE   LEAF 

the  morning.     Can  you  think  of  any  benefit  a  plant  might 

derive  from  this  habit  of  going  to  sleep  ? 

In  order  to  determine  whether  these  changes  are  due  to 

want  of  light  or  of  warmth,  put  your  plant   in    a  dark 

closet  in  the  middle  of  the 
day,  without  change  of  tem- 
perature. After  several 
hours  note  results.  Trans- 
fer to  a  refrigerator,  or  in 
winter,  place  outside  a  win- 
dow where  it  will  be  exposed 
to  a  temperature  of  about 
„  5°  C.  (40°  F.)  for  several 

103,  104.  —  Ground    pea   or    peanut:     J  / 

103,  in  day  position;  104,  in  night  posi-   hours,  and  see  if  any  change 

takes  place.     Next  put  your 

plant  at  night  in  a  well-lighted  room  and  note  the  effect. 
If  practicable,  keep  a  specimen  for  several  months  in 
some  place  where  electric  lights  are  burning  continuously 
all  night,  and  try  to  find  out  whether  it  is  possible  to  kill 
a  plant  for  want  of  sleep. 

64.  Autumn  Leaves.  —  When    trees  prepare   for   their 
winter  sleep  the  sap  all  retires  from  the  foliage  back  to  the 
stem  and  roots,  and  the  leaves,  having  no  more  work  to  do, 
give  up  their  chlorophyll  and  fall  away.     It  is  this  breaking 
up  of  the  chlorophyll  by  the  oxygen  of  the  air,  that  gives 
to  the  autumn  woods  their  brilliant  coloring,  and  not  the 
action  of  frost.     After  a  wet  season,  when  the  leaves  are 
full  of  sap  and  nourishing  juices,  the  chemical  changes 
attendant  upon  the  withdrawal  of  the  chlorophyll  are  more 
active,  and  the  changes  of  color  more  vivid  than  after  a 
period  of  drought,  when  the  leaves  wither  and  fall  away 
with  little  display  of  color. 

65.  The  Physiological   Significance   of   leaf   adjustment 
will  be  evident  if  we  consider  that  the  process  of  food 
manufacture  is  entirely  dependent  upon  the  action  of  chlo- 
rophyll through  the  agency  of  light.     Without  this  agency 
no  food  can  be  produced,  though  its  influence  is  not  always 


LEAF   ADJUSTMENT 


53 


direct.  Seeds  germinate,  bulbs  and  rootstocks  perform 
their  vegetative  functions,  and  many  parasites  and  sapro- 
phytes grow  and  flourish  in  the  dark,  but  in  these  cases  it 
is  always  at  the  expense  of  reserve  material  provided  by 
the  plant  itself,  or  by  the  host,  through  the  agency  of 
chlorophyll  acting  in  the  light.1  It  is  the  green  leaves  of 
summer  that  lay  up  the  stores  of  food  in  bulbs  and  root- 
stocks  for  winter,  and 
flowering  stems  will  even 
grow  and  blossom  in  the 
dark  if  enough  green 
leaves  are  left  exposed 
to  manufacture  nourish- 
ment for  them. 

Pass  the  end  of  a 
budding  flower  stem  of 
any  green-leaved  plant  — 
gourd,  squash,  water 
melon,  morning-glory, 
etc.,  make  good  examples 
—  through  a  small  hole 

into    a    dark   box,  leaving     105.  — A  gourd  plant  developed  partly  in  the 

the  rest  of  the  plant  ex-  dark  and  partly  in  the  light" 

posed  to  light,  and  taking  care  not  to  bruise  or  injure  it  in 
any  way.  Cover  the  entire  leafy  portion  of  another  plant 
of  the  same  kind  with  a  box,  leaving  only  the  flower  bud 
exposed,  and  covering,  or  cutting  away  any  new  leaves 
that  may  appear.  Watch  what  happens,  and  at  the  end 
of  two  or  three  weeks  compare  results.  The  green  plant 
may  not  show  any  change  for  several  weeks,  until  it 
has  used  up  the  chlorophyll  already  stored  away  in  its 
leaves. 

Experiments  like  the  foregoing  show  that  it  is  no  mere 
figure  of  rhetoric  to  speak  of  the  coal  hidden  away  in  the 
earth  as  "  stored  up  sunshine." 

1  Recent  discoveries  have  given  reason  to  believe  that  a  few  of  the  bacteria 
are  exceptions  to  this  statement,  but  with  regard  to  the  generality  of  plants,  it 
holds  true. 


54  THE   LEAF 

PRACTICAL  QUESTIONS 

i.   Why  are  the  outer  twigs  of  trees  generally  the  most  leafy?     (54, 

'2.   Is  the  common  sunflower  a  compass  plant?     Is  cotton? 

3.  Are  there  any  such  plants  in  your  neighborhood? 

4.  Compare  the  leaves  of  half  a  dozen  shade-loving  plants  of  your 
neighborhood  with  those  of  as  many  sun-loving  ones  ;  which,  as  a  gen- 
eral thing,  are  the  larger  and  less  incised? 

5.  Give  a  reason  for  the  difference.     (53,  56.) 

6.  Why  do  most  leaves  —  notably  grasses  —  curl  their  edges  back- 
wards in  withering?     (17,  60.) 

7.  What  advantage  is  gained  by  doing  this  ?     (60.) 

8.  Observe  such  of  the  following  plants  as  are  found  in  your  neigh- 
borhood, and  report  any  changes  of  position  that  may  take  place  in 
their  leaves  and  the  causes  to  which  such  changes  should  be  ascribed  : 
wood  sorrel,  mimosa  (Albizzid),  honey  locust,  wild  senna  (Cassia  ma- 
rilandica),  partridge  pea  (C.  chamachrista).  wild  sensitive  plant  (C.  nic- 
titans),  red  bud,  bush  clover  (Lespedeza),  Japan  clover  (L.  striata), 
Kentucky  coffee  tree,  sensitive  brier  (Schrankia),  ground  pea  or  peanut, 
kidney  bean. 

9.  Which  of  the  trees  named  below  shed  their  leaves  from  tip  to 
base  of  the  bough  (centripetally),  and  which  in  the  reverse  order?     Ash, 
beech,  hazel,  hornbeam,  lime,  willow,  poplar,  pear,  peach,  sweet  gum, 
elm,  sycamore,  mulberry,  China  tree,  sumac,  chinquapin. 


TRANSFORMATIONS   OF  LEAVES 

MATERIAL.  —  Any  kinds  of  leaves  that  can  be  obtained  showing 
adaptations  for  protective  and  other  purposes,  such  as  scales,  spines, 
tendrils,  glands,  etc.  Some  of  those  mentioned  in  the  text  are  :  sweet 
pea,  cedar,  cactus,  asparagus,  cabbage,  stonecrop,  purslane,  sarracenia, 
bladderwort  (Iftricularia),  sundew  (Drosera),  Spanish  bayonet 
( Yucca),  stinging  nettle  (Urtica),  horse  nettle  (Solatium  carolinense) . 
The  subject  is  best  studied  out  of  doors,  or  in  a  greenhouse. 

66.  Besides  performing   their  natural  functions,  leaves 
are   modified   in  various   ways  to  do  the  work  of  other 
organs.     No  part  of  the  plant  is  subject  to  more  curious 
and  varied  metamorphoses,  and  they  are  made  to  serve  all 
sorts  of  purposes. 

67.  Leaves  as  Tendrils.  —  Examine  a  leaf  of  the  wild 
vetch,  or  of  the  common  garden  pea,  and  it  will  be  seen 


TRANSFORMATIONS   OF   LEAVES  55 

that  the  two  or  three  upper  leaflets  are  transformed  into 
tendrils  for  climbing.  In 
the  sweet  pea  all  but  the 
two  lowest  leaflets  have 
been  developed  into  ten- 
drils. 

68.  Scale     Leaves. — 

Sometimes  the  leaf  disap- 
pears entirely,  or  is  reduced 
to  a  mere  scale  or  spine, 
as  in  the  cedar  and  most 
cactuses,  and  some  other 
part  takes  its  place,  but  it 
can  always  be  recognized 
by  its  position  on  the  stem, 
just  below  the  point  where 
a  bud  appears.  Ordinarily, 

buds  never  OCCUr  anywhere    i°6.- Leaf  of  common  pea,  showing  upper 
*  leaflets  reduced  to  tendrils. 

except  at  the  axil,  and  this 

position  is  so  constant  that  it  will  generally  serve  to  dis- 
tinguish leaves  from  other  organs  under  all  disguises. 
In  the  common  asparagus,  the  green  threadlike  appendages 
which  are  usually  regarded  as  foliage,  spring  each  from 
the  axil  of  a  little  scale.  This,  as  has  just  been  stated, 
is  the  normal  position  of  a  bud  or  branch,  and  hence, 
botanists  conclude  that  here  a  double  transformation  has 
taken  place,  of  leaves  into  scales  and  branches  into  foliage. 
Scale  leaves  are  of  use  to  plants  that  have  need  to  pro- 
tect themselves  against  frost  and  snow,  like  the  heaths  and 
mosses  of  cold  regions.  They  are  common  also  in  hot  and 
arid  districts  where  it  is  necessary  to  reduce  the  surface 
exposed  for  transpiration,  though  here  they  are  more  apt 
to  take  the  form  of  prickles  and  spines  as  a  double  protec- 
tion against  sun  and  animals. 

69.  Leaves  as  Storehouses  of  Food  and  Moisture.  —  Of 
this  we  have  familiar  examples  in  the  cabbage  and  other 


THE    LEAF 


107.  —  a,  Leaf  of  an  agave,  or 
American  aloe,  thickened  for  the 
storage  of  water;  b  and  c,  cross 
sections  made  at  points  indicated 
by  the  dotted  lines. 


salad  plants  of  the  garden.  In  some  of  the  fleshy  stone- 
crops  and  purslanes,  the  leaves 
seem  to  have  transformed  them- 
selves into  living  water  bags. 

70.  Death  Traps.  — The  sar- 
racenia,  better  known  as  the 
pitcher  plant,  or  trumpet  leaf, 
is  a  familiar  example  of  these 
vegetable  insect  catchers.  Its 
curious  pitcher-shaped,  or  trum- 
pet-shaped leaves  are  traps  for 
the  capture  of  the  small  game 
upon  which  the  plant  feeds. 
The  lower  part  of  the  blade  is 
transformed  into  a  hollow  vessel 
for  holding  water,  and  the  top 
is  rounded  into  a  broad  flap 
called  the  lamina.  Sometimes 

the  lamina  stands  erect,  as  in  the  common  yellow  trumpets 

of   our   coast   regions,  and  when   this   is  the  case,   it   is 

brilliantly    colored     and     attracts     insects. 

Sometimes,  as  in  the  parrot-beaked  and  the 

spotted  trumpet  leaf  (Fig.   108),  it  is  bent 

over  the  top  of  the  water  vessel  like  a  lid, 

and  the  back  of  the  leaf,  near  the  foot  of 

the  lamina,  is  dotted  with  transparent  specks 

that  serve  to  decoy  foolish  flies  away  from 

the  true  opening  and  tempt  them  to  wear 

themselves  out  in  futile  efforts  to  escape, 

as  we  often  see  them  do  against  a  window 

pane. 

If  the  contents  of  one  of  these  leaves  are 

examined  with  a  lens  there  will  generally 

be  found  mixed  with  the  water  at  the  bot- 

,  .  " 

torn,  the  remains  of  the  bodies  of  a  large 
number  of  insects.  Notice  that 'the  hairs 
on  the  outside  all  point  up,  towards  the  rim  of  the  pitcher, 


io8.  —  Spotted 

olaris]  :  /.lamina; 
s,  transparent  spots 


TRAiNSFORMATIONS   OF    LEAVES 


57 


while  those  on  the  inside  turn  downward,  thus  smoothing 
the  way  to  destruction  but  making  return  impossible  to 
a  small  insect  when  once  it  is  ensnared.  When  we 
remember  that  these  plants  are  generally  found  in  poor, 
barren  soil,  we  can  appreciate  the 
value  to  them  of  the  animal  diet 
thus  obtained. 

71.  Other  Examples  of  insect- 
catching  leaves  are  the  Venus's 
flytrap,  found  nowhere  but  in  a 
certain  section  of  North  Carolina, 
near  the  coast,  and  the  little  sun- 
dew (JDrosera  rotundifolia},  which 
Mr.  Darwin  has  made  the  heroine 
of  his  famous  book  on  "  Insectiv- 
orous Plants."  It  is  a  delicate, 
innocent  looking  little  flower,  and 
owes  its  poetic  name  to  the  dewlike 
appearance  of  a  shining,  sticky 
fluid  exuded  from  the  glands  on  its  leaves,  which  glitter  in 
the  sun  like  diamond  dewdrops.  It  is,  however,  the  most 


109. —  Plant  of  sundew. 


no.  —  Leaf  of  sundew  ex- 
panded. 


112.  —  Sundew  leaf  digest- 
ing a  meal. 


in.  —  Leaf  closing  over 
captured  insect. 


110-112.  —  Leaves  of  sundew  magnified. 

voracious  of  all  carnivorous  plants,  the  shining,  sticky 
leaves  acting  as  so  mariy  bits  of  fly  paper  by  means  of 
which  it  catches  its  prey.  When  a  fly  has  been  trapped, 


5  8  THE    LEAF 

the  edges  of  the  leaf  curve  inwards,  making  a  little  pouch 
or  stomach,  and  an  acid  juice  exudes  from  the  glands  and 
digests  the  meal.  After  a  number  of  days,  varying 
according  to  the  digestibility  of  the  diet,  the  blades  slowly 
unfold  again  and  are  ready  for  another  capture. 

In  the  bladderwort,  common  in  pools  and  still  waters 
nearly  everywhere,  the  petioles  are  transformed  into  floats, 
while  the  finely  dissected,  rootlike  blades  bear  little  bladders 
which,  when  examined  under  the  microscope,  are  found  to 
contain  the  decomposed  remains  of  captured  animalculae. 


1 13.  —  Bladderwort,  showing  finely  dissected  submerged  leaves  bearing  bladders 
ad  peuoles  transformed  to  a  whorl  of  floats  for  buoying  up  the  flowering  stem. 

72.  Protective  Leaves.  — One  of  the  most  frequent 
modifications  of  leaves  is  for  protection,  either  of  them- 
selves or  of  other  organs,  against  animals,  drought,  exces- 
sive moisture,  dust,  heat,  cold,  etc.  The  prickles  of  the 
thistle  and  horse  nettle,  the  hairs  of  the  stinging  nettle, 
and  the  sharp  spears  from  which  the  Spanish  bayonet 
(Yucca  aloifolia}  takes  its  name,  are  all  familiar  examples 

the  first  kind,  as  are  also  the  venom  of  the  poison  ivy 


TRANSFORMATIONS   OF   LEAVES 


59 


the  fetid  odors  of  the  jimson  weed  and  China  tree,  and 
even  the  aroma  of  the  pennyroyal  and  lavender  that  we 
pack  with  our  clothes  in  summer  to  keep  the  moths  away. 


114.  —  Protective  awl-pointed  leaves  of 
Russian  thistle. 


115.  —  Spine  protected  leaf  of  horse 
nettle. 


118.  PotentMa  cinerea. 


ug.   Shepherdia. 
116.  —  Spearlike  leaves  of  Spanish  bayonet.    117-119.  —  Protective  hairs  magnified. 


60  THE   LEAF 

The  protective  devices  of  leaves  are  generally  so  apparent 
that  the  student  can  easily  make  them  out  for  himself,  with 
the  help  of  a  few  suggestive  questions. 

PRACTICAL  QUESTIONS 

1.  How  can  it  benefit  a  plant  to  have  its  leaves,  or  some  of  them, 
changed  to  tendrils?     (67.) 

2.  What  advantage  to  plants  is  it  to  be  able  to  climb  ?    (54-57,  65 .) 

3.  Why  is  it  that  evergreen  trees  and  shrubs  have  generally  either 
thick,  hard,  coriaceous  leaves,  like  those  of  the  holly  and  magnolia,  or 
scales  and  needles,  as  in  the  cedar  and  pine?     (68.) 

4.  Why  are  winter  herbs  with  tender  foliage,  like  the  chickweed  and 
winter  cress,  generally  low  stemmed,  and  disposed  to  keep  close  to  the 
earth? 

5.  Why  do  many  plants  which  are  decidttous — that  is,  shed  their 
leaves  in  winter  —  at  the   north,  tend  to   become   evergreen   at   the 
south  ? 

6.  Question  5  seems  to  conflict  with  question  13,  page  27 ;  can  you 
reconcile  them? 

7.  Can  you  find  any  kind  of  leaf  that  is  not  preyed  upon  by  some- 
thing?   If  so,  how  do  you  account  for  its  immunity? 

8.  Make  a  list  of  some  of  the  most  striking  of  the  protected  leaves 
of  your  neighborhood. 

9.  What  is  the  nature  of  the  protective  organ  in  each  case? 

10.   For  protection  against  what  does  it  seem  to  be  specially  adapted? 

ir.  Are  the  plants  in  your  list  for  the  most  part  useful  ones,  or 
troublesome  weeds? 

12.  Examine  the  leaves  of  the  worst  weeds  that  you  know  and  see 
if  these  will  help  in  any  way  to  account  for  their  persistency. 


FIELD  WORK 

The  study  of  this  subject  and  of  all  those  that  follow  should  be  sup- 
plemented by  field  work,  in  expeditions  organized  for  the  purpose ; 
furthermore,  the  student  can  learn  a  great  deal  for  himself  by  keeping 
his  eyes  open  and  observing  the  plants  he  meets  with  in  his  ordinary 
walks. 

In  connection  with  Sections  14-30,  consider  the  effects  upon  soil 
moisture  of  water  transpiration  from  the  leaves  of  forest  trees  that  strike 
their  roots  deep,  and  from  those  of  shallow-rooted  herbs  and  weeds  that 
draw  their  water  supply  from  the  surface.  Consider  the  value  of  forests 
in  protecting  crops  from  excessive  evaporation  by  acting  as  wind 
breaks.  Study  the  effect  of  the  fall  of  leaves  on  the  formation  of  soil. 


TRANSFORMATIONS   OF   LEAVES  6 1 

I 

In  any  undisturbed  forest  tract  turn  up  a  few  inches  of  soil  with  a  gar- 
den trowel  and  see  what  it  is  composed  of.  Notice  what  kind  of  plants 
grow  in  it.  Note  the  absence  of  weeds  and  account  for  it.  Compare 
the  appearance  of  trees  scattered  along  windy  hillsides,  where  the  fallen 
leaves  are  constantly  blown  away,  or  in  any  position  where  the  soil  is 
unrenewed,  with  those  in  an  undisturbed  forest,  and  then  give  an 
opinion  as  to  the  wisdom  of  hauling  away  the  leaves  every  year  from  a 
timber  lot. 

Sections  31-49.  Observe  the  effect  of  the  lobing  and  branching  of 
leaves  in  letting  the  sunlight  through.  Notice  any  general  differences 
that  may  appear  as  to  shape,  margin,  and  texture  in  the  leaves  of  sun 
plants,  shade  plants,  and  water  plants,  and  account  for  them.  Study  the 
arrangement  of  leaves  on  stems  of  various  kinds  and  see  how  it  is 
adapted  in  each  case  to  the  shape  of  the  foliage.  Consider  the  value 
of  the  various  kinds  of  foliage  for  shade ;  for  ornament ;  as  producers 
of  moisture  ;  as  food ;  as  insect  destroyers,  etc. 

It  is  important  to  learn  to  know  and  distinguish  the  different  kinds  of 
trees  and  shrubs  in  your  neighborhood  by  their  leaves.  A  useful  exer- 
cise for  this  purpose  is  to  make  a  collection  of  those  of  some  family  like 
the  oaks  or  hawthorns,  that  contains  a  great  many  varieties,  and  com- 
pare them  carefully  with  one  another. 

Sections  50-65.  In  different  mosaics  and  rosettes  of  leaves  study 
the  means  by  which  the  adjustment  has  been  brought  about  and  the 
purpose  it  subserves.  Notice  the  form  and  position  of  petioles  of 
different  leaves,  and  their  effect  upon  light  exposure,  drainage,  etc.,  and 
the  behavior  of  the  different  kinds  in  the  wind.  Look  for  compass 
plants  in  your  neighborhood,  and  for  other  examples  of  adjustment  to 
heat  and  light.  Study  the  position  of  leaves  at  different  times  of  day 
and  in  different  kinds  of  weather  and  note  what  changes  occur  arid  to 
what  they  are  due.  The  sunflower  and  pea  families  offer  some  of  the 
most  striking  examples  of  this  kind  of  sensitiveness.  The  oxalis  and 
geraniums,  cotton,  and  others  of  the  mallow  family  ought  also  to  be 
investigated. 

Study  the  drainage  system  of  different  plants  and  observe  whether 
there  is  any  general  correspondence  between  the  leaf  drainage  and  the 
root  systems.  This  will  lead  to  interesting  questions  in  regard  to  irri- 
gation and  manuring.  (Where  plants  are  crowded  the  growth  of  both 
roots  and  leaves  is  complicated  with  so  many  other  factors  that  it  is 
best  to  select  for  observations  of  this  sort  specimens  growing  in  more 
or  less  isolated  situations.) 

Notice  the  time  of  the  expansion  and  shedding  of  the  leaves  of  differ- 
ent plants,  and  whether  the  early  leafers,  as  a  general  thing,  shed  early 
or  late ;  in  other  words,  whether  there  seems  to  be  any  general  time 
relation  between  the  two  acts  of  leaf  expansion  and  leaf  fall. 

Sections  66-72.     Look  for  instances  of  protected  leaves ;  study  the 


62  THE  LEAF 

nature  and  position  of  the  protective  organs  and  decide  as  to  their  special 
purpose,  whether  as  defenses  against  heat,  cold,  dust,  or  insects  and 
other  animals.  Examine  the  tendrils  of  various  climbing  plants  and  tell 
from  their  position  whether  they  represent  stipules,  leaves,  or  branches. 
Look  for  instances  of  transformed  leaves  of  any  kind  and  try  to  under- 
stand the  nature  and  object  of  the  transformation.  Always  be  on  the 
alert  for  transformations  and  disguises  everywhere,  and  account  for 
them  as  far  as  you  can. 


111.    FRUITS1 

FLESHY  FRUITS 

MATERIAL.  —  Apple,  pear,  haw,  hip,  or  other  pome  fruit ;  any  kind 
of  melon  or  gourd  fruit  (if  a  specimen  of  the  turban  squash  can  be 
obtained  it  will  illustrate  well  the  morphology  of  this  kind  of  fruit)  ; 
tomato,  cranberry,  lemon,  grape,  or  other  kind  of  berry;  a  pickled 
peach  or  cherry,  or  some  kind  of  wild  drupe,  as  dogwood  or  black  haw. 
City  schools  can  obtain  specimens  for  the  lessons  in  this  chapter  from 
fruit  stores,  and  teachers  can  do  a  great  deal  by  collecting  and  pre- 
serving material  when  on  their  summer  outings. 

73.  What  is  a  Fruit  ?  —  The  word  fruit  does  not  mean 
exactly  the  same  thing  to  the  botanist  that  it  does  to  the 
gardener   and   the  farmer.      Botanically,  a   fruit   is   any 
ripened  seed  vessel,  or  ovary,  as  it  is  technically  named, 
with  such  connected  parts  as  may  have  become  incorpo- 
rated with  it ;  and  so,  to  the  botanist,  a  boll  of  cotton,  a 
tickseed,  or  a  cockle  bur  is  just  as  much  a  fruit  as  a  peach 
or  a  watermelon. 

74.  The  Pome.  —  Examine  an  apple  or  pear.     With  the 
point  of  a  pencil  separate  the  little  dry,  pointed  scales  that 
cover  the  depression  in  the  center  of  the  end  opposite  to 
the  stem.     These  are  the  remains  of  the  sepals,  or  lobes  of 
the  little  green  cup  called  a  calyx  that  will  be  found  at  the 
base  of   all  apple  and   pear  blossoms  in  spring.     Their 

1  It  may  seem  a  little  premature  to  begin  the  study  of  fruits  here,  as  some 
kinds  cannot  be  fully  understood  without  examining  them  in  connection  with 
the  flower,  but  the  desirableness  of  taking  them  up  at  a  season  when  material 
is  abundant  seems  to  the  author  more  than  an  offset  to  this  objection.  It  will  be 
found  a  great  advantage,  moreover,  to  familiarize  the  pupil  with  the  structure 
of  the  ripened  ovary,  where  the  parts  are  large  and  easy  to  distinguish,  before 
taking  up  the  study  of  that  organ  in  the  flower,  where  it  is  often  so  small  that 
it  can  not  conveniently  be  dissected. 

63 


FRUITS 


nature  will  be  more  apparent  'on  comparing  them  with 
a  hip,  which  is  clearly  only  the  end  of  the  footstalk 
enlarged  and  hollowed  out  with 
the  calyx  sepals  at  the  top.  Cut 
a  cross  section  midway  between 
the  stem  and  the  blossom  ends, 
and  sketch  it.  Label  the  thin, 
papery  walls  that  inclose  the  seed, 
carpels.  How  many  of  them  are 
there,  and  how  many  seeds  does 
each  contain?  The  carpels  taken 

120. — Cross  section  of  a  pome:  ... 

//.placenta;  c. carpels ; / fibro-   together  constitute   fas  pericarp, 
vascular  bundles.  or  wan  of  tne  seed  vessel.     The 

fleshy  part  of  the  apple  is,  strictly  speaking,  no  part  of 
the  seed  vessel  or  ovary  proper,  but  consists  merely  of  the 
receptacle,  or  end  of  the  footstalk,  which  becomes  greatly 
enlarged  and  thickened  in  fruit.  The  word  pericarp,  how- 
ever, is  often  taken  in  a  broader  sense,  to  include  all  that 
portion  of  the  fruit  which  surrounds  and  adheres  to  the 
ovary,  no  matter  what  its^nature  or  texture.  Look  for  a 
ring  of  dots  outside  the  carpels,  connected  (usually)  by 
a  faint  scalloped  line.  How  many  of  these  dots  are  there  ? 
How  do  they  compare  in  number  with  the  carpels  ?  With 
the  remnants  of  the  sepals  ad- 
hering to  the  blossom  end  of 
the  fruit?  ^"^W  V 

f/     1L_  ,•••"' 

75.  Next  make  a  vertical  sec- 
tion through  a  fruit,  and  sketch 
it.  Notice  the  line  of  woody 
fibers  outside  the  carpels,  inclos- 
ing the  core  of  the  apple.  Com- 
pare this  with  your  cross  section  ; 
to  what  does  it  correspond  ? 

Where    do    these    threads     origi- 

nate?    Where  do  they  end  ?    Can    centa'- <-carPel- 

you  make  out  what  they  are  ?    (See  Section  43  ;  they  are  the 

fibrovascular  bundles  that  connected  the  veins  in  the  petals 


I2i.  —  Vertical  section  of  a 
pome :  p,  peduncle ;  f,  fibrovas- 
cular  bundles ;  s,  seeds ;  //,  pla- 


FLESHY    FRUITS  65 

and  sepals  of  the  apple  blossom  with  the  stem.)  Notice 
how  and  where  the  stem  is  attached  to  the  fruit.  Label 
the  external  portion  of  the  stem  peduncle,  the  upper  part, 
from  which  the  fibrovascular  bundles  branch,  the  torus, 
or  receptacle.  It  is  the  enlargement  of  this  which  forms 
the  fleshy  part  of  the  fruit.1  Try  to  find  out,  with  the  aid 
of  your  lens  and  dissecting  pins,  the  exact  spot  at  which 
the  seeds  are  attached  to  the  carpels,  and  label  this  point 
placenta.  Notice  whether  it  is  in  the  axis  where  the 
carpels  all  meet  at  their  inner  edges,  or  on  the  outer  side. 
Observe,  also,  whether  the  seed  is  attached  to  the  placenta 
by  its  big  or  its  little  end.  If  you  can  find  a  tiny  thread 
that  attaches  the  seed  to  the  carpel,  label  it  funiculus,  or 
seed  stalk. 

76.  Use  of  the  Rind.  —  Select  two  apples  of  equal  size, 
peel  one,  and  then  weigh  both.     After  twelve  to  twenty- 
four  hours,   weigh  them  again.      Which   has  lost  most  ? 
What  is  the  use  of  the  rind  ?     Place  peeled  and  unpeeled 
fruits  in  an  exposed  place  and  see  which  is  most  readily 
attacked  by  insects.     Which  decays  soonest  ? 

Write  under  the  sketches  that  you  have  made  the  word 
pome,  which  is  the  botanical  name  for  this  kind  of  fruit. 
Write  a  definition  of  a  pome. 

77.  Modifications  of  the  Pome.  —  Compare  with  the  draw- 
ings you  have  made,  a  haw  and  a  hip.     What  points  of 
agreement  do  you  see  ?     What  differences  ?    Which  of  the 
two  more  closely  resembles  the  typical  pome  ? 

The  pome  is  not  the  only  fruit  of  which  the  receptacle 
forms  a  part.  Other  well-known  instances  of  this  sort  of 
modification  are  the  fig,  lotus,  and  calycanthus  (see  Figs. 
123,  124);  but  a  fruit  is  not  a  pome  unless  the  containing 
receptacle  becomes  more  or  less  soft  and  edible.  The 
receptacle  is  subject  to  a  great  variety  of  modifications  and 
forms  a  part  of  many  fruits. 

1  See  Pome,  "  American  Encyclopedia  of  Horticulture,"  Macmillan  Co. 

ANDREWS'S    EOT.  —  5 


66 


FRUITS 


I22._  Vertical  section  of  123,  124.  —  Enlarged  receptacle  of  Caro- 

a    hip,   showing   seeds    con-  lina  allspice  (Calyca'nthus)  containing  fruits 

tained  in  a  hollow  receptacle  attached  to  its  inner  surface:    123,  exterior; 

(after  GRAY).  124,  vertical  section. 

78.  The  Pepo,  or  Melon.  —  Next  examine  a  gourd, 
cucumber,  squash,  or  any  kind  of  melon,  and  compare  its 
blossom  end  with  that  of  the  pome.  Do  you  find  any 
remains  of  a  calyx,  or  other  part  of  the  flower  ?  Examine 
the  peduncle  and  observe  how  the  fruit  is  attached  to  it. 
Cut  cross  and  vertical  sections,  and  sketch  them,  labeling 
each  part.  There  may  be  some  difficulty  in  making  out 
the  carpels,  for  they  are  not  separate  and  distinct  as  in  the 
pome,  but  confluent  with  the  enlarged  receptacle,  which 
in  these  fruits  forms  the  outer  portion  of  the  rind,1  and 
also  witrT  each  other  at  their  edges,  so  as  to  form  one 
unbroken  circle,  as  if  they  had  all  grown  together.  And 
this  is  precisely  what  has  happened. 
The  number  of  carpels  can  easily  be 
distinguished,  however,  by  counting 
the  placentas,  which  divide  the  interior 
into  compartments  called  cells  or  loculi, 
corresponding  in  number  to  the  num- 
ber of  carpels.  The  placentas  are 
greatly  enlarged  and  modified,  and  it 
may  be  necessary  to  refer  to  the  dia- 
gram, Figure  1 2  5,  in  order  to  make  them 
out.  How  many  cells,  or  chambers, 
are  there  in  your  specimen  ?  How  many  placentas  ?  Are 
the  seeds  vertical,  as  in  the  apple,  or  horizontal  ?  Look 

1  See  Cucurbita,  "  American  Encyclopedia  of  Horticulture." 


125. —  Cross  section  of 
gourd :  c,  one  of  the  car- 
pels in  diagram  (after 
GRAY). 


FLESHY    FRUITS 


126  127 

126,  127.  —  A  potato  berry: 

126,  exterior ;   127,  cross  section. 


for  the  little  stalk,  or  thread,  that  attaches  them  to  the 
placenta. 

Pepo  is  the  name  given  by  botanists  to  this  kind  of  fruit. 
Write  in  your  notebook  a  proper  definition  of  it,  from  the 
specimens  examined. 

79.  The  Berry.  —  Examine   a 
tomato,    an    eggplant,    a   grape, 
cranberry,  lemon,  or  orange,  in 
both  cross  and  vertical  section, 
and  compare  it  with  the  pepo. 
Notice    that    they    all    agree   in 
having  a  more  or  less  thick  and 
firm  outside  covering  filled  with 

a  soft,  pulpy  interior.     In  what  respects  does  the  one  you 

are  examining  differ  from  the  pepo  ? 

Fruits  of  this  kind  are  classed  by  botanists  as  berries. 

They  are  the  commonest  of  all  fleshy  fruits,  and  the  most 

variable   and   difficult   to    define.     In   general,    any   soft, 

pulpy,  or  juicy  mass, 
like  the  grape  and 
tomato,  whether  one  or 
many  seeded,  inclosed 
in  a  containing  envel- 
ope, whether  skin  or 
rind,  is  a  berry.  Its 

128,129.  —  Tangerine:  128,  vertical  section ;        typical   forms  are  Such 
129,  cross  section.  f      •  , 

fruits    as    the    grape, 

mistletoe,  pokeberry,  etc.,  though  such  diverse  forms  as 
the  eggplant,  persimmon,  red  pepper,  orange,  banana,  and 
pomegranate  have  been  classed  as  berries;  and,  in  fact, 
the  pepo  itself  is  only  a  greatly  modified  kind  of  the  same 
fruit.  In  popular  language,  any  small,  round,  edible  fruit 
is  called  a  berry,  but  do  not  confound  it  with 

80.  The  Drupe,  or  stone  fruit,  of  which  the  cherry,  plum, 
peach,  dogwood,  black  haw,  and  black  gum  furnish  typi- 
cal examples. 

Notice  that  the  drupe  agrees  with  the  berry  in  having 


68  FRUITS 

a  more  or  less  juicy  or  fleshy  interior   surrounded    by  a 
protecting   skin,  but  the  stone  within  this  is  not  a  mere 
seed,  such  as  we  find  in  the  berry,  but  con- 
sists of  the  inner  layer  of  the  pericarp,  which 
has  become  hard  and  bony.     Open  the  stone 
and   the   seed  will   be    seen   with   its   own 
coverings  inside.     Have   you  ever  found  a 
130. -Vertical    stone  with  more  than  one  kernel  to  it;   for 
section  of  a  drupe    jnstance,    in    eating    almonds?      This    fact 

(after  GRAY).  , 

shows  that  the  stone  is  not  a  seed  coat,  but 
the  hardened  inner  wall  of  a  seed  vessel  or  ovary ;  for 
a  seed  coat  can  never  contain  more  than  one  seed  any 
more  than  the  same  skin  can  contain  more  than  one 
animal.  In  a  green  drupe,  before  the  stone  has  hardened, 
its  connection  with  the  fleshy  part  is  very  evident.  This 
stony  layer  enveloping  the  seed  is  the  main  distinction 
between  the  drupe  and  the  berry,  and  it  is  not  always 
possible  to  make  it  out  except  by  an  examination  of  the 
young  ovary.  Of  course  there  can  be  but  one  stone  to 
a  carpel,  as  each  carpel  has  only  one  inner  coat  to  be 
hardened;  but  where  a  drupe  is  composed  of  several 
carpels  clustered  together,  as  we  saw  them  in  the  apple, 
each  one  may  produce  a  stone  from  its  inner  coat  while 
the  outer  coats  become  confluent,  as  in  the  melon,  and 
in  this  way  a  drupe  may  be  several  seeded,  as  is  actually 
the  case  in  the  dogwood,  elder,  etc. 

All  the  fruits  that  have  been  considered  in  Sections  73- 
80  belong  to  the  class  of  fleshy  ones.  These  form  the  great 
bulk  of  the  fruits  sold  in  the  market  and  served  upon  our 
tables,  and  are  of  special  importance  to  the  horticulturist. 


PRACTICAL  QUESTIONS 

1.  Examine  such  of  the  fruits  named  below  as  you  can  obtain,  and  tell 
to  which  of  the  four  kinds  described  each  belongs :  asparagus,  horse  nettle, 
China  berry,  smilax,  hackberry,  pawpaw,  guava,  persimmon,  red  pepper, 
orange,  buckeye,  gherkin,  pumpkin,  prickly  pear,  mangrove,  whortle- 
berry, banana,  date,  olive,  maypop,  cedar  berry,  Ogeechee  lime. 

2.  Which  are  the  commonest  of  fleshy  fruits  in  autumn? 


DRY   FRUITS  69 

3.  Name  six  of  the  most  watery  fruits  that  grow  in  your  neighborhood. 

4.  Under  what  conditions  as  to  soil,  heat,  moisture,  etc.,  does  each 
thrive  best? 

5.  Would  a  gardener  act  wisely  to  infer  that  because  a  fruit  contains 
a  great  deal  of  water  it  should  be  planted  in  a  very  wet  place? 

6.  Which  contains  most  water,  the  fruit  or  the  leaves  of  the  apple? 

7.  Why  does  the  fruit  not  wither  when  separated  from  the  tree,  as 
the  leaves  do?     (76.) 

DRY  FRUITS 

MATERIAL.  —  Acorn  or  other  nut ;  a  cotton  boll  or  a  pea  or  bean 
pod ;  various  small,  seedlike  fruits,  such  as  the  so-called  seeds  of  the 
sunflower,  carrot,  parsley,  clematis,  grains  of  corn,  etc. 

81.  Importance  of  Dry  Fruits.  —  Dry  fruits  are  not  in 
general  so  conspicuous  or  attractive  as  fleshy  ones,  but  on 
account  of  their  greater  number  and  variety  they  offer  a 
wide   field   for  study.     And    when  we  consider  that  the 
grains  which  furnish  our  breadstuffs,  and  the  beans  and 
nuts  that  form  so  large  a  part  of  our  food  all  belong  to 
this  class  we  realize  that  they  have  an  even  greater  claim 
upon  our  attention  than  the  most  brilliant  products  of  the 
garden. 

82.  Different  Kinds  of  Dry  Fruits.  —  Compare  an  acorn, 
a  chestnut,  or  a  hazelnut  with  a  ripe  cotton  boll  or  a  bean 
pod.     Try  to  open  each  with  your  fingers ;  what  difference 
do  you  perceive  ? 

This  difference  gives  rise  to  the  distinction  of  dry  fruits 
into 

83.  Dehiscent :  those  that  open  at  maturity  in  a  regular 
way  for  the  discharge  of  their  seed  ;  and 

84.  Indehiscent :  those  that  remain  closed  until  the  dry 
carpels  are  worn  away  by  decay,  or  burst  by  the  germina- 
tion of  the  contained  seed. 

85.  Why  Some  Fruits   Dehisce.  —  Open   each   of   your 
specimens ;  how  many  seeds,  or  kernels,  does  the  indehis- 
cent  one  contain  ?     The  dehiscent  one  ?     Can  you  explain 


FRUITS 


now  why  the  one  should  open  and  the  other  not  ?  Would 
it  be  of  any  advantage  for  a  one-seeded  pod  to  open? 
Remove  the  kernel  from  the  indehiscent  fruit  ;  has  it  any 
covering  besides  the  shell  ?  Which  is  the  pericarp,  and 
which  the  seed  coat  ? 

86.  Indehiscent   Fruits  are  so  simple  that  it  will  not  be 
necessary  to  devote  much  time  to  them.     Gather  specimens 
of  as  many  kinds  as  you  can  find,  and  try  to  identify  them 
by  means  of  the  pictures  and  descriptions  that  follow.    Do 
not  try  to  memorize  these  descriptions,  but  use  them  merely 
as  a  help  in  studying  actual  specimens.     The  acorn,  hick- 
ory nut,  chestnut,  etc.,  furnish  good  examples  of 

87.  The  Nut,  which   is  easily  recognized  by  its   hard, 
bony  covering,  containing  usually,  when  mature,  a  single 
large  seed  that  fills  the  interior.     Care  must  be  taken  not 
to  confound  with  true  nuts,  large  bony  seeds,  like  those  of 
the  buckeye,  horse-chestnut,  date,  and  the  Brazil  nut  sold 


131,   132.— Nut   of  the    pecan   tree:  133,    134.  —  N?utlike    seeds:     133, 

131,  exterior;  133,  cross  section.  horse-chestnut;  134,  seed  of  sterculia 

fcetida. 

in  the  markets.  In  the  true  nut  the  hard  covering  is  the 
seed  vessel,  or  pericarp,  and  no  part  of  the  seed  itself, 
though  it  often  adheres  to  it  so  closely  as  to  seem  so.  In 
bony  seeds  like  those  of  the  horse-chestnut  and  persimmon 
the  hard  covering  is  the  seed  coat.  The  distinction  is  not 
always  easy  to  make  out  unless  the  seed  can  be  examined 
while  still  attached  to  the  placenta  of  the  fruit. 

88.    The  Achene,  of  which  we  have  examples  in  the  tailed 
fruit  of  the  clematis,  the  tiny  pits  on  the  strawberry,  and 


DRY  FRUITS 


the  so-called  seeds  of  the  thistle,  dandelion,  etc.,  is  a  small, 
dry,  one-seeded  indehiscent  fruit, 
so  like  a  naked  seed  that  it  is 
generally  taken  for  one  by  per- 
sons who  are  not  acquainted  with 
botany.  It  is  the  commonest  of 
all  fruits,  and  there  are  so  many 
kinds  that  special  names  have  been 
applied  to  some  of  the  most  marked 
varieties.  The  achene  of  the  com- 
posite family  may  generally  be 

known  by  the  various  appendages 

in  the  form  of  scales,  hooks,  hairs, 

or  chaff,  that  crown  it  (Figs.  137- 

142).     This    appendage  is   always 

called  a  pappus,  no  matter  under 

what   form  it   occurs.      It   is   fre- 


135,  136.— Achenes  (magni- 
fied) :  135,  of  buckwheat;  136, 
of  cinquefoil. 


137 


139 


137-142.  —  Achenes  of  the  composite  family  (GRAY)  :  137,  mayweed  (no  pap- 
pus) ;  138,  chicory  (its  pappus  a  shallow  cup)  ;  139,  sunflower  (pappus  of  two 
deciduous  scales);  140,  sneezeweed  \Helenium),  with  its  pappus  of  five  scales; 
141,  sow  thistle,  with  its  pappus  of  delicate  downy  hairs;  142,  dandelion,  tapering 
below  the  pappus  into  a  long  beak. 


quently  deciduous,  as   in 


the  sunflower,  and  sometimes 
wanting  altogether,  as  in 
the  mayweed. 


89.   Cremocarp    is    the 

name  given  to  the  fruit 
of    the    parsley    family. 
I43  ,44  I45  It   is   merely   a   sort   of 

143-145.  —  Cremocarps,  fruits  of  the  parsley    double    achene     attached 

family'  by  the  inner  -faces  to  a 

slender  stalk  called  the  carpophore,  or  carpel  bearer,  from 


FRUITS 


which  it  separates  at  maturity.  Gather  a  fruiting  cluster 
of  fennel,  parsley,  caraway,  etc.,  and  examine  one  of  the 
small  seedlike  fruits  through  a  lens.  Separate  the  two 
achenes  of  which  it  is  composed,  and  find  the  carpophore 
between  them.  Sometimes  it  splits  in  two  (Fig.  145),  one 
half  going  with  each  achene ;  or  they  may  separate  from 
it  through  their  entire  length  and  remain  suspended  from 
the  top  (Fig.  144).  Notice  the  longitudinal  ribs  on  the 
back  of  the  achenes,  or  mericarps,  as  they  are  called. 
Between  these  ridges  are  situated  the  vittce,  or  oil  tubes  to 

which  the  aromatic 
flavor  of  these  fruits 
is  due. 


146,  147.  —  Samaras :  146, ; 


147 
lanthus ;  147,  maple. 


90.   The  Samara,  or 

key  fruit,  is  an  achene 
provided  with  a  wing 
to  aid  in  its  disper- 
sion by  the  wind. 
The  maple,  ash,  elm,  etc.,  furnish  familiar  examples. 

91.   The  Grain,  or  caryopsis,  so  familiar  to  us  in  all  kinds 

of  grasses,  is  a  modification  of  the 

achene  in  which  the  seed  coats  have 

so  completely  fused  with  the  pericarp 

that  they  can  no  longer  be  distin- 

guished  as   separate   organs.     Peel 

the  husk  from  a  grain  of  corn  that    view. 

has  been  soaked  for  twenty-four  hours,  and  you  will  find  the 

contents  exposed  without 
any  covering  ;  remove 
the  shell  of  an  acorn  or 
a  hickory  nut,  and  the 
seed  will  still  be  envel- 
oped by  its  own  coats. 


148, 149. — Grain  of  broom 
corn  millet  with  husks  on : 
148,  front  view;  149,  back 


Would  it  be  any  advan- 

r         ,,  ,       ,- 

taSG    f°r    the   seed    ot    an 

indehiscent  fruit,   like  a 
grain  of  corn  or  oats,  to  have  a  special  covering  of  its  own  ? 


151  **• 

150-152.  —  Gram  of  wheat:    150,  back  view  ; 
151,  front  view;  152,  front  view  (magnified). 


DEHISCENT  FRUITS  73 

92.  Distinction  between  Nuts  and  Achenes.  —  In  very 
small  fruits  it  is  not  easy  to  distinguish  between  a  nut  and 
an  achene,  nor  is  it  very  material.  Technically,  an  achene 
is  a  fruit  composed  of  a  single  carpel,  a  nut  of  two  or  more 
which  have  become  so  completely  fused  together  that  their 
separate  parts  can  be  detected  only  by  examining  the 
unripe  seed  vessel  in  the  flower.  Botanists  apply  the 
terms  very  loosely,  and  the  beginner  need  not  be  distressed 
if  he  can  not  classify  exactly  all  the  specimens  he  meets 
with.  In  general,  the  larger,  harder,  and  bonier  fruits  of 
the  kind  are  called  nuts.  The  family  to  which  a  speci- 
men belongs  must  also  be  taken  into  consideration.  For 
instance,  the  achene  being  the  characteristic  fruit  of  the 
sunflower  family,  any  puzzling  specimen  of  that  family, 
like  the  cockle  bur,  would  naturally  be  classed  as  an 
achene. 

PRACTICAL  QUESTIONS 

1.  Name  all  the  indehiscent  fruits  you  can  think  of  that  are  good 
for  food  or  other  purposes. 

2.  Make  a  list  of  the  commonest  indehiscent  fruits  of  your  neighbor- 
hood. 

3.  Which  of  these  are  useful  for  any  purpose? 

4.  Which  are  troublesome  weeds? 


DEHISCENT  FRUITS 

MATERIAL.  —  Simple  follicles  of  larkspur,  milkweed,  etc. ;  a  pod  of 
pea  or  bean  ;  pods  of  any  species  of  the  mustard  family,  or  of  the  trum- 
pet vine  (Tecoma)\  cotton,  okra,  iris,  or  Indian  shot  (Canna).  Cotton 
or  okra  are  preferable  if  they  can  be  obtained,  because  the  parts  are 
large  and  well  denned. 

93.  Simple,  or  Monocarpellary  Fruits.  —  Pod,  or  capsule, 
is  the   general  name   given  to  all   dehiscent  fruits.     The 
latter  term  is  properly  confined  to  pods  of  more  than  one 
carpel,  but  the  distinction  is  not  strictly  observed  by  bot- 
anists.    The  simplest  possible  kind  of  a  pod  is 

94.  The  Follicle,  of  which  the  larkspur,  milkweed,  marsh 
marigold,  etc.,  are  familiar  examples.     It  is  composed  of 


74 


FRUITS 


153.  —  Follicle  of  milk- 
weed. 


a  single  carpel,  which  may  be  regarded  as  a  modified  leaf. 
Examine  one  of  these  pods  and  you  will 
find  that  it  splits  down  one  side,  which 
corresponds  to  the  edges  of  the  leaf 
brought  together  and  turned  inwards  to 
form  a  placenta  for  the  attachment  of 
the  seed.  This  line  of 
union  is  called  a  suture, 
from  a  Latin  word 
meaning  a  seam. 

95.  The    Carpel    a 
Transformed     Leaf.  — 

The  leaflike  nature  of 

the  carpel  is  very  evi- 

dent in  such  fruits  as 
the  follicles   of   the   Japan  varnish  tree 
(Stemtlia  platanifolia\  where  even  the 
veining  is  quite  distinct,  and  the  whole       154.  —  Leaflike  foiii- 
carpel    so    leaflike    in    appearance    that   cle  of  Ja?an  varnish 

.  tree  :  s,  s,  sutures. 

there  is  no  mistaking  its  nature.     Indeed, 

after  the  wonderful  transformations  we  have  already  found 
leaves  undergoing,  their  development  into 
the  hardest  and  thickest  of  carpels  need 
not  surprise  us. 

96.  The  Legume.  —  Get  a  pod  of  any 
kind  of  bean  or  pea,  and  observe  that  it 
differs  from  the  follicle  in  having  two 
sutures  or  lines  of  dehiscence.  One  of 
these,  which  runs  along  the  back  of  the 
carpel  and  corresponds  to  the  midrib  of 
the  leaf,  is  called  the  outer,  or  dorsal,  su- 
ture ;  the  other,  corresponding  to  the 

Um'ted   edgGS   °f   the  CarPellarY   leaf.    is   the 

dorsal   inner,  or  ventral,  suture,  so  called  because 
it  always  turns   inwards,  that   is,  towards 
the  center  or.  axis  of  the  flower. 


suture;    d, 


DEHISCENT    FRUITS 


75 


97.  Origin  of  the  Name. — This  kind  of  pod  is  the  char- 
acteristic fruit  of  the  great  pea,  or  pulse  family,  and  gets 
its  name    from  the  Latin  word,  lego,  to  pick,  or  gather, 
because  crops  of  pulse  have  always  been  picked  by  hand 
instead  of  being  cut  or  mown  like  grain  and  hay. 

98.  Sutures.  —  Place  a  legume  upon  one  side  and  sketch 
it,  labeling  the  sutures.     If  you  cannot  tell  which  is  the 
dorsal  and  which  the  ventral,  open  the  pod  and  observe 
where  the  seeds  are  attached ;  this  is  the  ventral  suture, 
because  in  all  normal  carpels  it  is  the  united  edges  of  the 
leaf  margins,  or  in  other  words,  the  ventral  suture,  that 
forms  the  seed-bearing  surface,  or  placenta. 

99.  Valves.  —  Sketch  the  open  pod  with  the  seeds  in 
it,  showing  their  point  of  attachment.     Label  this  the//#- 
centa,  and   the  two  halves  into  which  the  pod  has   split, 
valves.     Notice  that  the  valves  are  not  separate  carpels, 

but  only  two  halves  of  the  same  carpel. 
What  is  the  difference  between  a  legume 
and  an  ordinary  follicle  ? 


157.  —  Legume  of  a  pea,  with 
partially  constricted  pod. 


158.  —  Loment  of  beggar's 
ticks. 


iS6.-Constric,ed  100'  The  Loment,  so  unpleasantly  famil- 
legume  of  cassia  iar  to  most  of  us  in  the  beggar's  ticks  tribe, 
is  merely  a  kind  of  legume  constricted 
between  the  seeds  and  breaking  up  into  separate  joints 
at  maturity.  What  kind  of  indehiscent  fruits  do  the  joints 
resemble  when  separated  ? 

101.    The  Silique  is  the  characteristic  fruit  of  the  mus- 
tard family,  as  the  legume  is  of  the  pea  tribe,  though  it  is 


76 


FRUITS 


common  in  other  plants  also,  the  trumpet  flower  (Tecoma 
radicans)  being  a  conspicuous  example.  Open  any  con- 
venient specimen  and  notice  the  manner  of  dehiscence. 
How  does  it  differ  from  that  of  the  legume  ?  What  other 
difference  do  you  perceive  ?  Are  the  edges  of  the  valves 
reflexed  or  folded  in  any  way  so  as  to  form  the  two  cells 
or  chambers  into  which  the  silique  is  divided  ?  How  is  the 
partition  made  ?  A  dividing  wall  of  this  sort,  that  is  made 
in  any  other  way  than  by  the  inflexed  margins  of  the  car- 
pels, is  called  a  false  partition.  Sketch 
your  specimen  as  it  appears  with  one 
of  the  valves  removed,  showing  the 
position  and  attachment  of  the  seeds. 
Where  is  the  placenta?  Is  the  false 
partition  parallel  with  the  valves  or  at 
right  angles  to  them  ?  Compare  it  in 
this  respect  with  other  specimens  of  the 
same  family,  and  with  the  silique  of  the 
trumpet  vine,  if  you 
can  get  one;  is  the 
159,160.— snique  of  direction  of  the  partl- 

mustard:  159    closed;     tjon    always   the  same? 

160,  alter   delnscence,  J 

showing     false    parti-     Does   it  fall    away  With 

tlon>^-  the    valves    or    remain 

161  162 

attached  to  the  receptacle?  161, 162.— Silicic  of 

shepherd's  purse :  161, 

102.  The  Silicle  is  only  a  short  and  entire;  162.  with  one 
broad   silique,    like   those   of   the   shep-  ^SSEtt 
herd's     purse    (Capsella     bursa-pastoris}  seeds,  and  the  false 
and  pepper  grass  (Lepidium}.     The  last  f^'t  ^ta^d 
two  named  belong  to  the  class  known  as  sides. 

103.  Syncarpous  or  Compound  Pods.  —  Generally  speak- 
ing, there  are  never  more  carpels  in  a  pod  than  there  are 
seed-bearing  sutures.     In  a  boll  of  cotton,  or  a  pod  of  okra, 
iris,  or  other  large  dehiscent  fruit,  notice  the  lines  or  seams 
running  from  base  to  apex  of  the  pericarp  ;  into  how  many 
sections  or  carpels  do  they  divide  it  ?     When  several  car- 
pels unite  in  this  way  into  one  body,  they  form  a  syncar- 


DEHISCENT  FRUITS 


77 


pous  pod  or  capsule — the  word  "syncarpous"  meaning  "of 
united  carpels."  The  three  large,  leaflike  bodies  at  the 
base  of  the  cotton  boll  (none  in  the  okra  —  unless  very 
immature  pods  are  used  —  or  the  iris)  are  bracts,  and  to- 
gether they  form  an  involucre.  Remove  these  and  also 
the  remains  of  the  flower  cup,  or  calyx,  that  will  be  found 
just  within  them,  and  notice  the  round,  flattish  expansion 
of  the  stem  where  the  fruit  is  attached.  Make  a  sketch  of 
the  closed  capsule,  labeling  this  expansion  receptacle,  the 
stem  itself  peduncle,  the  longitudinal  lines  sutures,  and  the 
spaces  between  them  carpels. 

Open  the  boll,  or  take  one  that 
has  already  dehisced,  remove 
the  lint  with  the  seed  from  two 
of  the  carpels,  allowing  them  to 
remain  in  the  others,  and  sketch 
the  whole  as  it 
appears  on  the  in- 
side. Notice  the 
protruding  ridge 
down  the  center  of 
each  carpel  which 
divides  the  fruit, 
when  closed,  into 
separate  chambers 
or  cells.  Find  out 
to  what  part  the  seeds  are  attached  and  label  it  placenta. 
The  little  threadlike  stalks  that  attach  the  seed  are 
very  small  and  hard  to  distinguish  from  the  fleece,  but 
when  they  are  broken  away,  their  place  can  generally  be 
detected  by  small,  toothlike  projections  on  the  placenta. 

In  pods  like  those  of  okra,  cotton,  iris,  etc.,  the  placenta 
is  said  to  be  parietal,  from  a  Latin  word  meaning  a  wall, 
because  it  projects  from  the  wall  of  the  seed  vessel.  From 
which  suture  does  it  arise,  the  dorsal  or  the  ventral  ? 
Which  kind  of  sutures  are  those  shown  on  the  exterior  of 
the  boll  ?  (Sees.  94,  98).  Does  it  dehisce  by  the  dorsal 
or  the  ventral  sutures  ?  Notice  that  when  a  capsule  splits 


163-166.  —  Capsule  of  okra  :  163,  entire,  c,  c,  car- 
pels, r,  receptacle,  s,  s,  sutures;  164,  vertical  section, 
//,  placenta,  o,  o,  ovules,  f,f,faniculus,  or  seed  stalk; 
165,  single  carpel;  166,  cross  section,  pi,  placenta, 
o,  o,  ovules,  s,  s,  sutures. 


78  FRUITS 

along  its  dorsal  sutures  in  this  way,  the  segments  into 
which  it  divides  are  made  up  of  the  two  contiguous  halves 
of  adjacent  carpels,  just  as  if  we  should  fasten  a  number 
of  leaves  together  by  their  edges  and  then  split  them  down 
their  midribs,  we  should  get  an  equal  number  of  sections 
made  up  of  the  adjacent  halves  of  different  leaves.  And 
on  the  supposition  that  carpels  are  altered  leaves,  this  is 
precisely  what  happens  in  the  case  of  syncarpous  capsules 
such  as  we  have  been  examining. 

104.  Modes  of  Dehiscence.  —  Make  a  diagram  of  the 
mode  of  dehiscence  of  your  specimen,  and  compare  it  with 
that  of  a  pod  of  the  castor  bean,  jimson  weed,  St.  John's- 
wort,  flax,  etc. ;  or  if  specimens  cannot  be  obtained,  with 
the  accompanying  diagrams.  What  difference  do  you 

perceive  in  their  modes  of  dehiscence? 

The  first  of  these  is  called 

105.  Loculicidal  (Fig.  167),  because  it 
splits  through  the  back  of  the  'carpels  di- 
rectly into  the  cells  or  loculi,  a  word  mean- 
ing "little  chambers."     The  second  is 

106.  Septicidal,  that  is,  the  dehiscence 
167-170.— Diagrams    takes  place  through  the  septa,  or  parti- 

of    dehiscence     (after       .  c 

GRAY):  167,  locuii-  tions  that  divide  the  cells  (Fig.  168). 
i^'and8'!^^:  Either  of  these  modes  may  become 

107.  Septifragal,   as   in  the    morning- 
glory,  where   the  carpels  break  away  from    the  division 
walls,   leaving   them    attached   to  the   axis   of   the   fruit 
(Figs.     169    and     170). 

Another  common  form 
is  the 

108.  Circumscissile, 
in  which  the  upper  part 
of  the  pod  comes  off  like 
the  lid  of  a  dish,  as  in 
the  purslane,  plantain 
henbane,  amaranth,  etc! 


DEHISCENT   FRUITS 


79 


109.   Union  of  Carpels.  —  The  carpellary  leaves  may  unite 
either  by  their  open  edges,  as  if  a  whorl  like  that  repre- 
sented in  Figure  77,  were  to  grow  together  by  the  margins 
(Fig.  173);   or  each  may  first  roll  itself 
into  a  simple   follicle  like  the   larkspur 
and   columbine  (Fig.    175),  and   then    a 
number    of    these    may    unite   by   their 
ventral  sutures  into  a  single  syncarpous 


173. —  Plan  of  one-celled 
ovary  formed  by  the  union 
of  open  carpellary  leaves 
(GRAY). 


174.  —  Cross  section  of 
one-celled  syncarpous  cap- 
sule of  frostweed,  with 
parietal  placentae  (GRAY) . 


175. —  Follicles  of 
larkspur  borne  on 
the  same  torus,  but 
distinct. 


capsule,  with  as  many  cells  as  there  are  carpels  (Fig.  177). 
The  seed-bearing  sutures  being  all  brought  together  in  the 
center,  the  placenta  becomes  central  or  axial.  In  the  first 


176.  —  Podsofeche- 
veria,  contiguous,  but 
distinct. 


177.  —  Capsule  of  col- 
chicum,  with  carpels  united 
into  a  syncarpous  pod. 


178.  —  Capsule  of  corn 
cockle,  with  free  axile 
placenta. 


case  (Fig.  174)  the  open  carpels  form  a  one-celled  capsule, 
though  the  placentas  sometimes  project,  as  in  the  cotton 
and  okra,  so  far  as  to  produce  the  effect  of  true  partitions 
with  central  placenta  (Fig.  164).  In  one-celled  capsules, 


8o 


FRUITS 


the  number  of  carpels  can  generally  be  determined  by 
the  number  of  sutures  or  of  placentas.  The  placenta 
is  not  always  formed  by  the  margins  of  the  carpels,  how- 
ever, but  sometimes  the  seeds  are  borne  upon  a  prolonga- 
tion of  the  receptacle,  as  in  the  pink  and  the  corn  cockle 
(Fig.  178),  forming  *  free  central  placenta.  A  free  central 
placenta  may  also  be  formed  when  the  carpels  of  a  pod 
break  away  from  the  seed-bearing  surface,  as  in  Figures 
169  and  170. 

PRACTICAL  QUESTIONS 

1.  Can  you  name  any  syncarpous,  or  compound  capsule  that  is  single- 
seeded  ? 

2.  Can  you  name  any  indehiscent   fruit   that   has  more   than  one 
seed? 

3.  Name  the  weeds  of  your  neighborhood  that  are  most  troublesome 
on  account  of  their  adhesive  fruits. 

4.  Do  they  belong,  as  a  general  thing,  to  the  dehiscent  or  the  inde- 
hiscent class  ? 

5.  Give  a  reason  for  these  facts. 


ACCESSORY,  AGGREGATE,   AND   COLLECTIVE  FRUITS 

MATERIAL.  —  If  snake  strawberries  (Fragaria  indica),  Osage  orange, 
and  other  late  fruits  of  the  kind  cannot  be  obtained,  a  pineapple  may 
be  used  for  the  whole  class.  Fresh  figs,  if  they  can  be  obtained,  make 
good  objects  for  study,  but  dried  ones  may  be  used.  Hips,  haws, 
etc.,  are  always  plentiful  at  this  season.  As  many  of  the  fruits  men- 
tioned in  the  Practical  Questions  as  can  be  obtained  should  be  studied 
either  in  or  out  of  class. 

110.  Besides   the   varieties    already   named,    all   fruits, 
whether  fleshy  or  dry,  may  be  either  simple,  accessory, 
aggregate,  or  collective.     The  first  kind  need  no  explana- 
tion;    they    consist    merely   of    a   single    ripened    ovary, 
whether  of  one  or  more  carpels,  as  the  peach,   cherry, 
bean,  lemon,  etc. 

111.  Accessory  Fruits  are  so  called  because  some  other 
part  than  the  seed  vessel,  or  ovary  proper,  is  coherent 
with  or  accessory  to  it  in  forming  the  fruit,  as  we  saw  in 


ACCESSORY,  AGGREGATE.  AND  COLLECTIVE  FRUITS     8 1 


179-181. — Sections  of  accessory 
fruits  of  strawberry  and  black- 
berry, showing  enlarged  receptacle 
(after  GRAY):  179,  strawberry; 
180,  blackberry;  181,  separate 
drupe  of  blackberry  (magnified). 


the  apple  and  the  hip.  The  accessory  part  may  consist  of 
any  organ,  but  is  more  frequently 
the  calyx  or  the  receptacle.  In 
the  strawberry,  the  little  hard 
bodies,  usually  called  seeds,  that 
dot  the  surface,  are  the  true 
fruits  (achenes).  A  vertical 
section  through  the  center  will 
show  the  edible  part  to  consist 
wholly  of  the  enlarged  recep- 
tacle. In  the  pineapple,  the 
edible  stalk  may  be  traced 
straight  through  a  mass  of 
flowers  whose  seed  vessels  have  become  enlarged  and 
ripened  into  fruits.  Some  accessory  fruits,  the  strawberry 
and  blackberry  for  example,  are,  at  the  same  time, 

112.  Aggregate,  that  is,  they 
are  composed  of  a  number  of 
separate  individual  fruits  pro- 
duced from  a  single  flower. 
The  cone  of  the  magnolia  and 
of  the  wild  cucumber  are  aggre- 
gate fruits ;  can  you  name  any 
others  ?  The  pineapple,  on  the 
other  hand,  is  both  an  accessory 
and  a 


rj  n 

182  183        184 

182-184. — Aggregate  fruit  of 
magnolia  umbrella  (after  GRAY)  : 
182,  ripened  cone  with  a  seed  hang- 
ing from  a  lower  dehiscent  carpel ; 


113.   Collective,     or     Multiple 

183,  vertical  section;    184,  separate     Fruit     being    composed     of     the 

follicle. 

ripened  seed  vessels  or  ovaries 

of  a  number  of  separate  flowers  that  have  become  more 
or  less  coherent.  The  osage  orange,  sweet-gum  balls,  fig, 
and  mulberry  are  of  this  class. 

114.  Flower  Fruits.  —  Compare  a  section  through  a  fig 
with  those  of  the  hip  and  calycanthus  (Figs.  122,  124). 
Of  what  is  the  part  that  we  call  the  skin  a  modification  ? 
Observe  that  here  the  receptacle  is  modified  to  a  greater 

ANDREWS'S    BOT.  —  6 


82 


FRUITS 


degree  than  in  the  rose  and  calycanthus,  forming  a  sort  of 
closed  urn  in  which  the  flowers  are  contained.  Examine 
the  contents  with  a  lens,  and  it  will 
be  found  that  they  consist  of  hun- 
dreds of  what  appear  to  be  tiny 
seeds  enveloped  in  a  pulpy  mass, 
but  which  are,  in  reality,  the  small 
achenes  produced  by  a  multitude  of 
minute  flowers  that  line  the  recep- 
tacle. In  the  fig  this  entire  mass 
becomes  pulpy  and  edible  at  matu- 
flowers  inside  the  closed  rity,  so  that  we  only  state  a  fact  when 
we  commit  the  hibernicism  of  saying 

that  the  fruit  of  the  fig  is  a  flower  —  or  rather,  a  bunch 
of  flowers.  The  same  is  true  of  the  mulberry,  only  here 
the  edible  flower  mass  is  attached  not  to  the  inside,  but 
to  the  outside  of  the  receptacle. 

The  fig  and  strawberry  are  both  accessory  fruits ;  which 
of  them  is  collective  also,  and  which  aggregate?  The 
mulberry  and  blackberry?  Is  it  possible  always  to  dis- 
tinguish between  an  aggregate  and  a  collective  fruit  without 
having  examined  the  flower  ? 

115.    Fruit  Clusters.  —  Be  careful  not  to  confound  aggre- 
gate and  collective  fruits  with  mere  clusters  like  a  bunch 
of   grapes   or   of   sumac   berries.      The 
distinction  is  not  always  easy  to  make        ^\^JWK$9Kfc._ 
out     The  clump  of  achenes  that  make 
up  a  dandelion  ball,  for  instance,  though 
held  on  a  common  receptacle,  like  the 
mulberry  and  other  collective  fruits,  have 
so  little  connection  with  each  other,  and 
separate   so  completely  at   maturity  as 
to  partake  more  of  the  nature  of  a  cluster 
than  of  a  collective  fruit.     The  same  is 
true  of  the  clump  of  tailed  achenes  that    i86.-Head  or  duster 
make    up    the    fruit    of    the    clematis. 
Though  the  product  of  a  single  flower,  and  thus  techni- 


ACCESSORY,  AGGREGATE,  AND  COLLECTIVE  FRUITS     83 

cally  an  aggregate  fruit,  they  are  really  only  a  compact 
head  or  cluster.  Some  degree  of  cohesion  is  necessary  to 
constitute  a  cluster  of  matured  ovaries  into  an  aggregate 
or  a  multiple  fruit. 

116.  The  Individual  Fruits  that  make  up  the  various 
kinds  just  described  may  belong  to  any  of  the  classes  men- 
tioned in  Sections  73-109;   those  of  the  blackberry,  for 
instance,  are  drupes;  of  the  strawberry,  achenes ;  of  the 
sweet  gum,  capsules. 

117.  Use  of  Fruits  to  the  Plant.  —  Have  you  ever  asked 
yourself  how  it  could  benefit  a  plant  to  invite  birds  and 
beasts  to  devour  its  fruit,  as  so  many  of  the  bright  berries 
we  find  in  the  woods  seem  to  do  ? 

In  order  to  answer  this  question  we  must  remember  that 
it  is  clearly  to  the  advantage  of  every  plant  to  disperse  its 


187-190.  —  Fruits  adapted  to  wind  dispersal :  187,  winged  pod  of  pennycress ; 
188,  spikelet  of  broom  sedge ;  189,  achene  of  Canada  thistle ;  190,  head  of  rolling 
spinifex  grass. 

seeds  as  widely  as  possible,  both  that  the  seedlings  may 
have  plenty  of  elbow  room,  and  that  they  may  not  have 
to  draw  their  nourishment  from  soil  already  exhausted  by 
their  parents.  The  farmer  recognizes  this  principle  in 
the  rotation  of  crops,  because  he  knows  that  successive 
growths  of  the  same  plant  will  soon  exhaust  the  soil  of 
substances  proper  for  its  nutrition,  while  they  may  leave 
it  rich  in  nourishment  suitable  for  a  different  crop.  Now, 
Nature,  like  a  good  farmer,  seeks  to  provide  for  a  rotation 


84 


FRUITS 


in  her  crops  by  furnishing  all  sorts  of  devices  for  the 
widest  possible  distribution  of  seeds.  In  the  case  of  fleshy 
fruits  this  object  is  accomplished,  for  the  most  part, 
through  the  agency  of  animals.  Our  cultivated  fruits 
have  been  so  altered  by  man,  and  the  parts  useful  to  him- 
self developed  so  exclusively  for  his  own  benefit  that  we 
cannot  always  judge  from  them  exactly  what  service  any 
particular  organ  would  render  to  the  plant.  But  in  a  state 
of  nature,  where  the  struggle  for  existence  is  so  severe,  no 
species  can  afford  to  develop  any  organ  or  quality  that  is 


194  196 

191-196.  — Adhesive  fruits:  191,  pod  of  wild  licorice;  192,  cockle  bur;  193, 
achene  of  bur  marigold  ;  194,  burdock  bur ;  195,  fruit  of  hound's  tongue ;  196, 
ffuit  of  bur  grass  (Cetic&rus). 

not  useful  to  itself.  Hence,  if  you  will  examine  the  wild 
fruits  of  your  neighborhood  you  will  find  that  the  edible 
ones  generally  produce  hard,  bony  seeds,  either  too  small 
to  be  destroyed  by  chewing,  and  thus  capable  of  passing 
uninjured  through  the  digestive  system  of  an  animal;  or 
if  too  large  to  be  swallowed  whole,  compelling  the  animal, 
by  their  hardness,  or  by  their  disagreeable  flavor,  to  reject 
them. 

On  the  other  hand,  where  the  seeds  themselves  are  edi- 
ble or  attractive,  the  fruits  are  armed  in  every  possible 


ACCESSORY,  AGGREGATE,  AND  COLLECTIVE  FRUITS    85 

way  against  the  assaults  of  animals.  The  acidity  or  other 
disagreeable  qualities  of  most  unripe  fruits  —  the  persim- 
mon for  instance  —  insures  them  pretty  effectually  against 
being  molested  before  they  have  had  time  to  mature  their 
seeds,  while  in  nuts  and  other  indehiscent  fruits,  the  pro- 
tection afforded  by  their  bony  pericarp  is  frequently  ree'n- 
forced  during  the  growing  season  by  such  appendages  as 
the  bur  of  the  chestnut  and  the  astringent  hulls  of  the 
walnut  and  hickory  nut. 

The  adaptations  for  dispersal  in  dry  fruits  consist  mainly 
of  wings  and  sails,  like  those  of  the  maple,  ash,  thistle, 
dandelion,  etc.,  by  which  they  are  carried  from  place  to 
place  by  the  wind  or  water;  or  of  hooks  and  adhesive 
hairs  by  means  of  which  they  attach  themselves  to  the 
coats  of  animals  or  the  clothing  of  men,  who  are  thus 
made  the  involuntary,  and  often  the  unwilling  agents  of 
their  dispersal. 

PRACTICAL  QUESTIONS 

1.  To  what  class  of  fruits  would  you  refer  an  ear  of  corn?  of  wheat? 
a  sycamore  or  a  buttonwood  ball?  a  hop?  a  raspberry?   a   bunch  of 
bananas?  a  pine  cone?  the  fruit  of  the  tulip  tree  and  umbrella  tree?  of 
the  mallow?  Indian  turnip? 

2.  Tell  the  nature  of  the  individual  fruits  that  compose  each. 

3.  Name  some  fruits  that  are  adapted  to  be  carried  about  by  the 
wind  ;  by  water ;  by  animals. 

4.  How  is  the  watermelon  fitted  for  seed  dispersal?  the  squash? 
fig  ?  hickory  nut  ?  huckleberry  ?   pomegranate  ?  maypop  (Passiflora  in- 
carnata)'!  corn?  wheat?  oats? 

5.  Could  the  last  three  survive  in  their  present  form  without  the 
agency  of  man? 

6.  Name  all  the  plants  you  can  think  of  that  bear  samaras  and 
winged  fruits  of  any  kind ;  are  they,  as  a  general  thing,  tall  trees  and 
shrubs,  or  low  herbs? 

7.  Name  all  you  can  think  of  that  bear  adhesive  fruits,  like  the 
cockle  bur  and  beggar's  ticks  ;  are  any  of  these  tall  trees  or  shrubs  ? 

8.  Give  a  reason  for  the  difference. 

9.  Why  is  the  dandelion  one  of  the  most  widely  distributed  weeds 
;n  the  world? 

10.  Why  is  it  that  appendages  for  protection  and  dispersal  are  con- 
nected with  the  pericarp  in  indehiscent  fruits  and  with  the  seeds  in  the 
dehiscent  kinds? 


86  FRUITS 


FIELD  WORK 

Study  the  various  edible  fruits  of  your  neighborhood  with  regard  to 
their  means  of  dissemination  and  protection.  Consider  the  object  of 
the  protective  devices  in  each  case,  whether  against  heat,  cold,  moisture, 
animals,  etc. 

Compare  wild  with  cultivated  fruits  and  notice  in  what  respects  man 
has  altered  the  latter  for  his  own  benefit.  Note,  for  instance,  the  differ- 
ence between  cultivated  apples  and  the  wild  crab,  between  the  culti- 
vated grains  and  wild  grasses.  Observe  the  great  number  of  varieties  of 
each  kind  in  cultivation  and  try  to  account  for  it. 

Notice  the  situations  in  which  different  kinds  of  fruits  grow,  whether 
hot,  dry,  moist,  windy,  or  sheltered,  etc.,  and  how  they  are  affected  by 
their  surroundings. 

Notice  what  animals  feed  upon  the  different  kinds,  and  whether  their 
visits  are  harmful  or  beneficial.  Consider  in  what  respects  the  inter- 
ests of  the  plant  itself,  the  interests  of  man,  and  the  interests  of  other 
animals  mav  clash  or  coincide. 


IV.     SEEDS   AND    SEEDLINGS 

MONOCOTYLEDONS  AND  POLYCOTYLEDONS 

MATERIAL.  —  Dry  and  soaked  grains  of  corn  and  oats,  or  other 
grasses.  Seed  of  pine;  the  cones  should  be  gathered  in  September 
or  October,  and  kept  until  needed. 

118.  Dissection  of  a  Grain  of  Corn.  —  Examine  a  dry  grain 
of  corn  on  both  faces.  Sketch  the  grooved  side,  labeling 
the  hard,  yellowish  outer  portion,  endosperm,  the  depression 
near  the  center,  embryo,  or  germ. 

Next  take  a  grain  that  has  been  soaked  for  twenty-four 
to  twenty-six  hours.  What  changes  do  you  see  ?  How  do 
you  account  for  the 
swelling  of  the  embryo  ? 
Remove  the  skin  and 
observe  its  texture.  Is 
it  a  pericarp,  a  seed 
coat,  or  both  ?  (Sec.  91.)  ^7  198 

Sketch     the     grain     with  197-199.  -  Dissection  of  a  grain  of  corn 
(GRAY)  :  197,  soaked  grain,  seen  flatwise,  cut 

the   COat   removed,  label-  away  a  little  and    slightly  enlarged,  so  as  to 

•           fu       fl    t             i     L    j  show  the   embryo  lying   in   the   endosperm; 

mS    *                                      ^  198,   in    profile    section,    dividing    the    grain 

embedded    in    the    eildo-  through  the  embryo  and  cotyledon;   199,  the 

+    J  J         4-U  embrvo  taken  out  whole.     The  thick  mass  is 

sperm,  cotyledon,  the  up-    the  cotvledon.   the  narrow  body  projecting 

per  end  of  the  little  bud-      upwards,  the  plumule;  the  short  projection  at 

like  body  embedded  in  the  base>  the  hypocoty1' 
the  cotyledon,  plumule,  the  lower  part,  hypocotyl — words 
meaning  respectively,  "seed  leaf,"  "little  bud,"  and  "the 
part  under  the  cotyledon."  As  this  part  has  not  yet  dif- 
ferentiated into  root  and  stem,  we  can  not  call  it  by  either 
of  these  names.  The  cotyledon,  the  hypocotyl,  and  the 
plumule  together  compose  the  embryo.  Pick  out  the 
embryo  and  sketch  it  as  it  appears  under  the  lens,  then 
87 


SEEDS    AND    SEEDLINGS 


remove  the  plumule  with  the  hypocotyl  from  the  cotyle- 
don, and  sketch  it.  Make  a  vertical  section  of  another 
soaked  grain  at  right  angles  to  its  broader  face,  and  sketch 
it,  labeling  the  parts  as  they  appear  in  profile.  Make  a 
cross  section  through  the  middle  of  another  grain,  and 
sketch  it.  (A  very  sharp  instrument  must  be  used  in 
making  sections,  or  they  will  not  be  satisfactory.) 
What  proportion  of  the  grain  is  endosperm  and  what 
embryo  ? 

It  has  been  seen  that  one  of  the  effects  of  iodine  is  to 
turn  starch  blue,  or  even  black  (Sec.  26).     Put  a  drop  on 
some  of  the  endosperm  and  note  the 
effect.      Of    what    does    it    consist? 
0  KM-H-SH       Test  tne  seec*  coats  in  the  same  way 
t  fP-^l        to  see  if  they  contain  any  starch. 

119.  Study    of    a    Typical    Small 
Grain.  —  Make  a  similar  examination 
of  a  grain  of  oats  or  wheat.    Compare 
the  endosperm  of  a  soaked  grain  with 
200, 201.— Dissection  of    that  of  an  unsoaked  one;  what  change 

200,  entire,      hag    taken    place     and     h()w     ^Q     ^ 

account  for  it  ?     Test  with  iodine  and 
see  what  it  consists  of.     Which  con- 


enlarged, 

showing  c,  cotyledon,  p, 
plumule,  A,  hypocotyl;  201, 
vertical  section,  c,  coty- 
ledon, e,  endosperm,  /,  tains  the  greater  proportion  of  endo- 

plumule,  A,  hypocotyl.  , 

sperm,  wheat  (or  oats)  or  corn  ? 

Notice  that  both  the  kinds  of  grain  just  examined  have  but 
one  cotyledon,  hence,  such  seeds  are  said  to  be  mono- 
cotyledonous.  The  grains  are  not  typical  seeds  (Sec.  91), 
but  are  selected  for  examination  because  they  are  large 
and  easy  to  obtain,  and  germinate  readily.  Other  mono- 
cotyledonous  seeds  should  be  examined  if  practicable. 
The  blackberry  lily  (Belamcanda}  and  iris  furnish  good 
examples. 

120.  Polycotyledons.  —  Remove  one  of  the  scales  from 
a  pine  cone  and  sketch  the  seed  as  it  lies  in  its  place  on 
the  cone  scale.  The  seed  with  its  wing  looks  very  much 


MONOCOTYLEDONS  AND  POLYCOTYLEDONS    89 

like  a  samara  of  the  maple,  but  it  differs  from  all  forms 

of  the  achene  in  being  a  true  seed  and  not  a  fruit.     Notice 

that  the  pine  has  no  closed  seed  vessel, 

or   ovary,   like   the  other  specimens  we 

have  been  considering,  but  bears  its  seed 

naked  in  the    axil   of   the   cone   scales, 

which  may  be  considered  open  carpels. 

Hence,  plants   of   this   kind   are   called 

Gymnosperms,  a  word  that  means  "naked        ^' *ao    _  ^3tch 

Seeds."  pine    seeds    (GRAY): 

Look  at  the  bottom,  or  little  end  of  ^mei^whh  one  seed 
the  seed,  with  your  lens,  for  a  small  in  place;  203,  winged 

TI  •       11  T\/r    i  seed,  removed. 

opening  like  a  pm  hole.     Make  an  en- 
larged drawing  of  the  seed  as  it  appears  under  the  lens, 
labeling  this   hole  micropyle,  a  Greek  word  meaning  "  a 
little  gate,"  because  it  is  the  entrance  to 
the  interior  of  the  seed. 

Remove  the  coat  from  a  seed  that  has 
been  soaked  for  twenty-four  hours,  and 
examine  it  with  a  lens.     Pick  out  the 
embryo  from  the  endosperm.     Does  the 
^    endosperm  resemble  that   of   the   corn 
tyiedonous"   embryo    and   wheat  ?     Test    it   with    iodine    for 
starch.      How    does  the  embryo   differ 
from   those   already  examined?      How  many  cotyledons 
are  there  ? 

Plants  having  more  than  two  seed  leaves  are  said  to  be 
polycotyledonous,  a  word  meaning  "  having  many  cotyle- 
dons." This  structure  is  characteristic  of  the  pines,  firs, 
hemlocks,  and  some  other  plants,  mostly  belonging  to  the 
Gymnosperms,  or  naked-seeded  class. 

PRACTICAL  QUESTIONS 

1.  What  gives  to  Indian  corn  its  value  as  food?     To  oats;  wheat; 
barley;  rye;  rice?     (118,  119.) 

2.  Which  of  these  grains  have  the  larger  proportion  of  starch  or 
other  endosperm  to  the  embryo? 

3.  Do  the  husks  or  seed  coats  contain  any  nourishment? 


g0  SEEDS   AND   SEEDLINGS 

4.  Is  there  any  nourishment  in  the  embryos,  apart  from  the  endo- 
sperm ? 

5.  What  is  bran? 

6.  Why  will  hogs  fatten  in  a' pine  thicket  in  autumn? 


DICOTYLEDONS 

MATERIAL.  —  Dry  and  soaked  seeds  of  the  common  bean,  cotton, 
and  castor  bean.  Where  cotton  can  not  be  obtained,  okra,  maple,  ash, 
morning-glory,  or  any  other  convenient  specimens  may  be  used,  pro- 
vided they  are  selected  so  as  to  show  both  the  albuminous  and  the  ex- 
albuminous  structure.  Squash,  pumpkin,  horse-chestnut,  etc.,  also 
make  good  studies.  Beans  should  be  put  to  soak  from  12  to  24  hours 
before  used ;  cotton  about  48 ;  squash  and  pumpkin  from  3  to  5  days, 
and  very  hard  seeds  like  the  okra,  castor  bean,  and  morning-glory 
from  7  to  10.  If  such  seeds  are  clipped  before  soaking,  that  is,  if  a 
small  piece  of  the  coat  is  chipped  away  from  the  end  opposite  the  scar, 
they  will  soften  more  quickly.  Keep  them  in  a  warm  place  with  an 
even  temperature  till  just  before  they  begin  to  sprout,  when  the  con- 
tents become  softened.  Very  brittle  cotyledons  may  be  softened  quickly 
by  boiling  them  for  a  few  minutes. 

121.  Examination  of  Some  Typical  Seeds.  —  Take  a  bean 
from  the  pod,  noticing  carefully  its  point  of  attachment. 
Lay  it  on  one  side  and  sketch  it,  then  turn  it  over  and 
draw  the  narrow  edge  that  was  attached  to  the  pod. 
Notice  the  rather  large  scar  (commonly  called  the  eye  of 
the  bean)  where  it  broke  away  from 
the  point  of  attachment.  Label  this 
in  your  drawing,  hilum.  Just  below 
,h  the  hilum,  look  for  a  minute  round 
pore  like  a  pin  hole.  Label  this 
micropyle.  Compare  a  soaked  bean 
TO.  with  a  dry  one ;  what  difference  do 

205.  206-A  kidney  bean  :     ^  Perceive  ?       How  do  you  account 

205,  side  view;  206,  rhaphai  for  the  change  in  size  and  hardness  ? 
Find  the  hilum  and  the  micropyle  in 
the  soaked  bean.  Make  a  section 
through  the  long  diameter  at  right  angles  to  the  flat  sides, 
press  it  slightly  open  and  sketch  it.  Notice  the  line  or 
slit  that  seems  to  cut  the  section  in  half  longitudinally,  and 


DICOTYLEDONS  91 

the  small  round  object  between  the  halves  at  one  end;  can 
you  tell  what  it  is  ? 

Slip  off  the  coat  from  a  whole  bean  and 
notice  its  texture.  Hold  it  up  to  the  light 
and  see  if  it  shows  any  signs  of  veining. 
See  whether  the  scar  at  the  hilum  extends 
through  the  kernel,  or  marks  only  the  seed 
coat.  Does  the  coat  seem  to  adhere  to 
the  kernel  more  firmly  at  one  point  than  207.  — Cotyledon 
another  ?  If  so,  label  this  point  chalaza.  °[ a  b^an-  showins 

J  plumule. 

Lay  open  the  two  flat  bodies  into  which  the 
kernel  divides  when  stripped  of  its  coats.  Sketch  their 
inner  face  and  label  them  cotyledons.  Be  careful  not  to 
break  or  displace  the  tiny  bud  packed  away  between  the 
cotyledons,  just  above  the  hilum.  Label  the  round,  stem- 
like  portion  of  this  bud,  hypocotyl,  and  the  upper,  more 
expanded  part,  plumule.  Which  way  does  the  base  of  the 
hypocotyl  point,  toward  the  micropyle,  or  away  from  it? 
Pick  out  this  budlike  body  entire  and  sketch  as  it  appears 
under  the  lens.  Open  the  plumule  with  a  pin  and  exam- 
ine it  with  a  lens  ;  of  what  does  it  appear  to  consist  ?  Do 
you  find  any  endosperm  around  the  cotyledons  as  in  the 
corn  and  oats  ?  Break  one  of  the  soaked  cotyledons, 
apply  some  iodine  to  it,  and  report  whether  it  contains 
any  starch.  Where  is  the  nourishment  for  the  young  plant 
stored  ?  What  part  of  the  bean  gives  it  its  value  as  food  ? 

Notice  that  in  the  bean  the  embryo  consists  of   three  x 
parts,  the  hypocotyl,  plumule,  and  cotyledons,  which  com-    i 
pletely  fill  the  seed  coats,  leaving  / 
no  place  for  endosperm. 

122.    Dissection    of    a    Cotton 
Seed. — (Where  cotton  can  not 
-cotton  seed  with  lim.        b^     obtained,    morning-glory, 
okra,  or   maple  may  be   used.) 

Scrape  the  lint  from  a  seed  of  cotton  as  closely  as  pos- 
sible, or  if  practicable,  get  a  specimen  of  one  of  the  smooth 
seeded  varieties  in  cultivation,  and  look  for  a  faint  line  or 


SEEDS  AND   SEEDLINGS 


groove  on  one  side,  leading  from  the  small  end  to  the  big 
end.  Make  a  sketch  of  the  side  showing  this  line,  label 
it  rhaphe,  and  the  point  where  it  begins,  at  the  large  end 
of  the  seed,  chalaza.  Look  for  the  hilum  at  the  other 
end  of  the  rhaphe,  and  for  the 
micropyle  near  it,  at  the  small 
end  of  the  seed.  If  they  can 
not  be  distinguished  on  account 
of  the  lint,  make  a  longitudinal 
section  of  a  well-soaked  seed 
and  find  where  the  hypocotyl 

209,210.  — Dissected  cotton  seed:     pomts.         Which     wav      did      it 

209,  seed  with  lint  removed  (magni-     ^    .        ,  '   .     . 

fied  three  times).  /  funiculus,  or  point  in  the  bean  t  1  hlS  IS  the 
seed  stalk,  r,  rhaphe,  ch.  chalaza;  casg  wjth  aU  seeds  the  bage 

210,  cross  section  of  the  seed  still 

more  highly  magnified,  showing  the  of  the  hypOCOtyl  is  towards 
crumpled  cotyledons.  the  micropyle)  and  so  we  can 

always  tell  where  the  micropyle  is  by  noticing  which  way 
the  hypocotyl  points.  Make  an  enlarged  sketch  of  the 
section  as  it  appears  under  the  lens,  and  also  of  a  cross 
section  of  another  soaked  seed  about  midway  between  the 
two  ends,  showing  as  accurately  as  you  can  the  lines  of 
any  folds  or  convolutions  that  you  may  see.  Label  such 
parts  as  you  can  clearly  make  out,  leaving  the  others  till 
after  further  examination. 

From  a  seed  that  has  been  boiled  for  five  or  ten  minutes 
to  soften  the  contents,  gently  remove  the  coats  so  as  to 
leave  the  embryo  whole.  How  many  seed  coats  are 
there  ?  How  do  they  differ  in  color  and 
texture  ?  Try  to  distinguish  them  in 
the  sketches  you  have  made,  and  label 
the  hard  outer  one  that  corresponds 
to  the  shell  of  an  egg,  testa,  the  soft  2II._Embryo  with 
inner  one,  tegmen.  What  is  the  use  of  cotyledons  partly  un- 
each  ?  As  the  coats  were  removed  did  folded- 
they  seem  to  adhere  to  the  kernel  more  tenaciously  at 
one  point  than  elsewhere?  Look  for  a  little  dark  spot 
inside  near  the  base,  that  marks  where  the  seed  coats  and 
kernel  adhered  together.  Refer  to  your  sketch  of  the  out- 


DICOTYLEDONS  93 

side  of  the  seed,  and  say  to  what  it  corresponds.  Are 
the  chalaza  and  micropyle  close  together,  as  in  the  bean, 
or  at  opposite  ends  of  the  seed  ? 

Sketch  the  kernel,  or  embryo,  without  opening  it,  as  it 
appears  under  the  lens.  Notice  the  irregular  fold  or 
groove  down  one  side  that  divides  it  into  two  nearly  equal 
parts.  Label  these  cotyledons.  Observe  the  complicated 
way  in  which  they  are  folded.  Try  to  imitate  it  with  a 
piece  of  paper.  Would  any  other  way  of  folding  fit  them 
so  snugly  into  the  seed  coats?  Straighten  them  out  as 
well  as  you  can  and  sketch  them.  Which  are  most  leaf- 
like,  the  cotyledons  of  the  bean  or  the  cotton  ?  Are  either 
of  them  at  all  similar  in  shape  to  the  foliage  leaves  of  their 
respective  plants  ?  How  do  they  compare  in  size  relatively 
to  the  size  of  the  respective  seeds  ?  Which  are  best  fitted 
to  perform  the  office  of  true  leaves  ? 

In  seeds  like  the  pea  and  bean,  where  the  cotyledons 
are  too  thick  and  clumsy  to  do  well  the  work  of  true  leaves 
the  young  plant  will  need  a  well-developed  plumule  to 
begin  life  with,  but  where  the  cotyledons  are  thin  and 
leaflike,  as  in  the  cotton,  and  to  a  less  degree  in  the  pump- 
kin and  squash,  and  capable  of  developing  quickly  into 
true  leaves,  there  is  generally  no  plumule  formed  in  the 
embryo. 

123.  The  Castor  Bean.  —  Lay  a  castor  bean  on  a  sheet 
of  paper  before  you  with  its  flat  side  down ;  what  does  it 
look  like?  The  resemblance  may  be  increased  by  soak- 
ing the  seed  a  few  minutes,  in  order  to  swell  the  two  little 
protuberances  at  the  small  end.  Can  you  think  of  any 
benefit  a  plant  might  derive  from  this  curious  resemblance 
of  its  seed  to  an  insect  ? 

Sketch  the  seed  as  it  lies  before  you,  labeling  the  pro- 
tuberance at  the  apex,  caruncle.  The  caruncle  is  no 
essential  part  of  the  seed,  but  a  mere  appendage  devel- 
oped by  various  plants,  the  use  of  which  is  not  always 
clear.  What  appears  to  be  its  object  in  the  castor  bean  ? 
It  may  occur  on  any  part  of  the  seed,  though  it  generally 


94 


SEEDS   AND   SEEDLINGS 


takes  some  other  name  when  borne  elsewhere  than  at  the 

micropyle,  of  which 
it  is  usually  an  out- 
growth. 

Turn  the  seed  over 
and  sketch  the  other 
side.  Notice  the 
colored  line  or  stripe 
that  runs  from  the 

212-214.  —  Castor  bean   (slightly  magnified):  ,  ,  , 

212,  back  view;    213,  front  view,  cA,  chalaza,  r,  large       end       to       the 

rhaphe,  ca,  caruncle ;  214,  vertical  section,  e,  em-  caruncle.  This  repre- 
bryo,  en,  endosperm. 

sents  the  rhaphe.    Its 

starting  point  near  the  large  end,  which  is  marked  in  fresh 
seeds  by  a  slight  roughness,  is  the  chalaza.  Where  the 
rhaphe  ends,  just  at  the  beak  of  the  caruncle,  you  will  find 
the  hilum.  The  micropyle  is  covered  by  the  caruncle, 
which  is  an  outgrowth  from  it. 

Next  cut  a  vertical  section  through  a  seed  that  has  been 
soaked  for  several  days,  at  right  angles  to  the  broad  sides, 
and  sketch  it.  Label  the  thick  outer  coat  testa,  the  deli- 
cate inner  one  tegmen,  the  white,  pasty  mass  within  that, 
endosperm.  Can  you  make  out  what  the  narrow  white  line 
running  through  the  center  of  the  endosperm,  dividing  it 
into  two  halves,  represents  ?  Make  a  similar  sketch  of  a 
cross  section.  Notice  the  same  white  line  running  hori- 
zontally across  the  endosperm,  dividing  it  into  two  equal 
parts.  To  find  out  what  these  lines  are,  take  another  seed 
(always  use  soaked  seeds  for  dissection)  and  remove  the 
coats  without  injuring  the  kernel.  Notice  the  little  dark 
spot  where  it  was  joined  to  the  coats  at  the  chalaza.  Split 
the  kernel  carefully  round  the  edges,  remove  half  the 
endosperm,  and  sketch  the  other  half  with  the  delicate 
embryo  lying  on  its  inner  face.  You  will  have  no  diffi- 
culty now  in  recognizing  the  lines  in  your  drawings  as 
sections  of  the  thin  cotyledons.  Where  is  the  hypocotyl, 
and  which  way  does  its  base  point  ?  Remove  the  embryo 
from  the  endosperm,  separate  the  cotyledons  with  a  pin, 
and  hold  them  up  to  the  light  to  see  their  beautiful  texture. 


DICOTYLEDONS  95 

Sketch  them  under  the  lens,  showing  the  delicate  venation. 
Is  there  any  plumule  ? 

Test  the  endosperm  with  a  little  iodine  to  see  if  it 
contains  any  starch.  Crush  a  bit  of  it  on  a  piece  of  white 
paper  and  see  if  it  leaves  a  grease  spot.  What  does  this 
show  that  it  contains  ?  Test  the  embryo  in  the  same  way, 
and  see  whether  it  contains  any  oil. 

124.  Arrangement  of  the  Embryo.  —Notice  the  difference 
in  the  way  the  embryo  is  packed  in  the  castor  bean,  and 
in  such  seeds  as  the  cotton,  okra,  and  maple.  In  the 
former  it  is  said  to  be  straight,  while  in  the  latter  it  is 


215  216  217  218 

215-218.  —  Arrangement  of  embryo  in  endosperm  (GRAY):  215,  morning-glory; 
216,  barberry ;  217,  potato ;  218,  four  o'clock. 

folded  or  plicate.  In  different  seeds  it  may  be  coiled  and 
folded  in  many  different  ways.  It  may  also  be  packed 
within  the  endosperm,  as  the  castor  embryo,  or  coiled  or 
wrapped  around  it,  as  in  the  chickweed. 

125.  Storage  of  Nourishment  in  the  Seed.  —  In  the  various 
seeds  examined  we  have  seen  that  the  nourishment  for 
the  young  plant  is  either  stored  in  the  embryo  itself,  as  in 
the  cotyledons  of  the  bean,  acorn,  squash,  etc.,  or  packed 
about  them  in  the  form  pf  endosperm,  as  in  the  corn, 
wheat,  and  castor  bean. 

The  latter  are  classed  by  botanists  as  albuminous,  the 
former  as  ex-albuminous — the  word  "albumin"  referring  not 
to  the  chemical  composition  of  the  food  supply,  but  to  its 
office,  which  is  similar  to  that  of  the  albumen,  or  white  of 
the  egg  stored  up  for  the  nourishment  of  the  hatching 
chick.  The  older  botanists,  recognizing  the  analogies 
between  the  seed  and  the  egg,  and  not  understanding  the 
true  nature  of  either,  regarded  the  seed  as  a  sort  of  vege- 


96  SEEDS   AND   SEEDLINGS 

table  egg,  and  named  the  reserve  material  we  now  call 
endosperm,  albumen.  It  is  now  known  to  be  something 
very  different,  however,  from  the  white  of  an  egg.  Fre- 
quently it  is  starch,  as  we  have  seen  in  the  corn,  wheat, 
oats,  etc.,  or  it  may  be  an  oil,  as  in  the  castor  bean  and 
peanut,  or  something  quite  different  from  either.  Hence, 
modern  botanists  have  renamed  this  substance  endosperm, 
a  word  meaning  merely  something  contained  "  within  the 
seed,"  and  therefore  applicable  to  any  kind  of  substance. 
The  old  adjectives,  albuminous  and  ex-albuminous,  have 
been  retained  for  want  of  something  better  —  ex-endo- 
spermous  being  such  an  awkward  compound  that  even 
botanists  hesitate  to  use  it. 

By  far  the  greater  number  of  seeds  are  albuminous ; 
that  is,  they  consist  of  an  embryo  with  more  or  less  nour- 
ishing matter  stored  about  it  in  various  ways.  Even  in 
ex-albuminous  seeds  the  endosperm  is  present;  it  has 
merely  been  absorbed  and  stored  in  the  cotyledons  before 
germination. 

126.  Principles  of  Classification.  —  We  are  now  prepared 
to   understand   the   great   fundamental   distinctions  upon 
which  botanists  base  their  classification  of  Spermatophytes, 
or  seed-bearing  plants.     The  first  division   depends  upon 
the  presence  or  absence  of  a  seed  vessel,  and  ranges  all 
the  higher  plants  into  two  classes  according  to  this  fea- 
ture.    The  first  division  embraces  the 

127.  Gymnosperms,  or  naked-seeded  plants,  of  which  we 
have  had   an  example  in   the   pine.     They  are  the  most 
primitive  type  of  seed-bearing  plants  and  the  most  ancient. 
Though  they  are  not  so  abundant  now  as   in  past  ages, 
numbering  only  about  four  hundred  known  species,  they 
present  many  diversities  of  form,  which  seem  to  ally  them 
on  the  one  hand  with  the  lower,  or  spore-bearing  plants 
(ferns,  mosses,  etc.),  and  on  the  other  with  the 

128.  Angiosperms,  or  plants  that  produce  their  seeds  in 
a  special  covering  of  closed  carpels,  like  most  of  the  fruits 


DICOTYLEDONS  97 

and  pods  that  we  have  been  considering.  This  group 
contains  all  the  true  flowering  plants,  and  forms  the  most 
important  part  of  the  vegetation  of  our  globe,  numbering 
not  less  than  one  hundred  thousand  species.  It  is  divided 
into  two  great  groups,  distributed,  as  we  have  seen,  accord- 
ing to  the  number  of  their  cotyledons,  into 

129.  Monocotyledons  and  Dicotyledons.  —  These  are 
further  distinguished  by  the  fact  that  dicotyledons  have, 
as  a  general  thing,  net-veined,  and  monocotyledons,  parallel- 
veined  leaves.  The  cause  of  this  difference,  science  has 
never  yet  been  able  to  explain,  so  that  for  the  present  we 
shall  have  to  accept  it  as  a  fact  which  we  can  not  under- 
stand. There  are  other  differences,  also,  in  the  structure 
of  the  flower  and  the  stem,  which  will  be  considered  later. 


PRACTICAL  QUESTIONS 

I.   Make  a  list  of  all  the  seeds  you  can  think  of  that  have  very  thick 
cotyledons. 

i.    Draw  a  line  under  all  that  are  used  as  food  by  man  or  beast. 

3.  Could  a  species  derive  any  advantage  from  tempting  animals  to 
eat  and  destroy  its  seed ?     (n/-) 

4.  What  then  is  the  advantage  to  the  plant  of  providing  this  food 
"supply?     (125.) 

5.  Do  you  find  any  edible  seeds  without  protection,  and  if  so, 
account  for  their  want  of  it. 

6.  Make  a  list  of  all  the  albuminous  seeds  you  can  think  of  that  are 
used  for  food  or  other  purposes,  such  as  medicines  and  unguents. 

7.  Do  you  find  as  many  food  materials  among  these  as  among  the 
ex-albuminous  kind? 

8.  Are  they  in  general  as  well  protected  as  ex-albuminous  seeds? 

9.  How  do  the  two  compare,  in  a  general  way,  as  to  size  ? 

10.  What  part  of  the  following  plants  do  we  eat,  the  fruit  or  the 
seed  ?     Corn  ;    wheat ;    hickory  nut ;    cocoanut ;    Brazil  nut ;    peanut ; 
beechnut;  string  beans;  honey  locust ;  coffee;  anise;  celery. 

1 1 .  From  what  part  of  the  castor  bean  do  we  get  the  oil  ?     Of  the 
peanut?     Of  the  cotton  seed?  % 

12.  What  gives  to  cotton-seed  meal  its  value  as  cattle  food? 

13.  Is  there  any  valid  objection  to  the  wholesomeness  of  peanut  oil, 
and  cotton-seed  lard? 

ANDREWS'S    EOT.  —  7 


98 


SEEDS   AND   SEEDLINGS 


FORMS  AND  GROWTH  OF   SEED 

MATERIAL.  —  Various  kinds  of  pods  and  fruits  with  the  seed  still 
attached  to  the  placentas,  such  as  the  following.  Straight  seeds : 
buckwheat,  smilax,  dock,  knotweed.  Inverted :  castor  bean,  cotton, 
violet,  magnolia,  cherry,  apple,  and  the  majority  of  common  seeds. 
Curved:  bean, purslane,  jimson  weed, okra,  and  most  of  the  pink  family. 

130.  Erect  Seeds.  —  The  most  natural,  and  at  the  same 
time  the  least  common  mode  of  attachment  is  for  a  seed  to 
stand  erect  upon  its  stalk  like  a  pink  or  a 
rosebud  on  its  stem.  A  seed  that  grows 
in  this  manner  is  said  to  be  orthotropous 
(Figs.  220,  221).  If  we 
imagine  the  seed  coats  to 
be  separated  from  each 
other  and  from  the  em- 

219.  —  An  erect     ,  ,         , . 

flower,    showing   bryos,  as  in  the  diagram 

attachment  of  the     (Fig.     22O),    WC     shall    SCC 

that    the    parts  all   come 

together  and  coalesce  at  the  base,  where 

they  are  attached  to  the  seed  stalk,  just 

as  all  the  parts  of  a  flower  adhere  at 

the  receptacle  (Fig.  221).  This  point, 
the  organic  base  of  the 
seed,  is  the  chalaza,  and 
you  can  now  understand  the  tendency  of 
the  coats  of  the  different  seeds  examined 
to  cohere  there.  An  inspection  of  the 
diagram  will  show  that  in  orthotropous 
seeds  the  hilum  and  chalaza  will  always 
coincide.  At  the  other  end,  the  tip  or 
apex  of  the  seed  (Fig.  220),  the  coats  do 
not  quite  come  together,  thus  causing  the 
sma11  aPerture  that  we  labeled  "micropyle" 

showing  insertion  of   in   our   drawings.       In    this    arrangement 

GR^Y)!  baSC  (after    the  micropyle  will  always  be  opposite  the 
chalaza,  and   it  marks  the    organic   apex 

of  the   seed  as  the  chalaza  does  its  base. 


220.  —  Diagrammatic 
section  of  a  typical 
or  orthotropous  seed 
(GRAY),  showing  the 
outer  coat,  a;  the  in- 
ner, b\  the  nucleus,  c; 
the  chalaza,  or  place 
of  junction  of  these 
parts,  d. 


FORMS  AND  GROWTH  OF  SEED 


99 


131.  Inverted  Seeds.  —  But  sometimes  a  flower  turns 
over  on  its  stalk,  like  the  snowdrop  and  harebell,  and  the 
same  thing  often  happens  to  a  seed.  This  gives  rise  to 
the  inverted,  or  anatropous  kind  (Fig.  223).  In  this  case, 
which  is  due  to  certain  peculiarities  in  the  early  growth  of 
the  seed,  the  stalk  does  not  remain  separate  like  the  stem 
of  a  pendent  flower,  but  coalesces  more 
or  less  completely  with  the  coats,  and 
thus  forms  the  rhaphe  (Fig.  223),  d.  The 
chalaza  remains  at  the  base,  ch,  which  is 
now  by  inversion  at 
the  top;  but  as  the 
stalk,  or  rhaphe,  is 
adherent  to  the  coats,  222  _  A  pendulous 
it  can  not  break  away  flower,  showing  the 
at  the  base,  and  invertedP°si 
hence,  in  anatropous  seeds  the  hilum 
and  micropyle  are  brought  close  to- 
gether, at  the  real  apex  of  the  seed. 
The  adherent  stalk,  or  rhaphe,  often 
223.—  Diagram  of  an  becomes  reduced  to  a  mere  line  or 

inverted     or     anatropous 

seed,  showing  the  parts  in    groove,  as  we  saw  in  the  cotton  and 

section:   a,  outer  coat;  b,     castor    bean      or    may    disappear    altO- 
inner    coat;     c,    nucleus; 

d,  rhaphe;    ch,  chalaza;    gether,  but  the  chalaza  can  generally 
be    distinguished   by   a   tendency   of 
the  parts  to  cohere  at  that  point. 
Variations  in  these  modes  of  attachment  are  shown  in 
Figures  225,  226.     In  the  campylotropous  or  curved  kind, 
the  seed  is  bent  over  during  early  growth  into  a  circular  or 
kidney  shape,  so  that  the  micropyle  is  brought  into  close 


m 


mkropyle 


•t  W_/      » — M^ / 

224  225  226  227 

224-227.  —  Seeds  (GRAY) :  224,  orthotropous  seed  of  buckwheat,  c,  hilum  and 
chalaza,  /  micropyle;  225,  campylotropous  seed  of  a  chickweed,  c,  hiiuin  and 
chalaza,  f,  micropyle;  226,  amphitropous  seed  of  mallow,  f,  micropyle,  h,  hilum, 
r,  rhaphe,  c,  chalaza ;  227,  anatropous  seed  of  a  violet,  the  parts  lettered  as  in  the  last 


I00  SEEDS   AND   SEEDLINGS 

juxtaposition  with  the  hilum,  as  we  saw  in  the  bean.  How 
does  this  differ  from  the  anatropous  kind  ?  Compare  the 
seed  you  have  examined  and  the  drawings  you  have  made 
with  Figures  224-227,  and  see  if  you  can  tell  to  which 
class  each  belongs.  Why  are  these  distinctions  not  appli- 
cable to  corn  and  other  grains  ?  (Sec.  91). 

132.  Position  in  the  Pericarp.  —  The  terms  "orthotro- 
pous,"  "anatropous,"  etc.,  refer  to  the  position  of  the  seed 
on  its  footstalk  and  have  nothing  to  do  with  its  attachment 


228  229  230 

228-230.  —  Position  of  seeds  in  the  carpels:  228,  erect  seed  of  Ceanothus;  229, 
horizontal  anatropous  seeds  of  the  European  star-of-Bethlehem ;  230,  suspended 
seeds  of  Polygala. 

to  the  pericarp,  which  may  be  either  erect,  horizontal,  or 
suspended.  An  orthotropous  seed  may  hang  bottom  up- 
wards from  the  apex  of  the  carpel  without  altering  its 
character ;  and  in  like  manner  one  of  the  anatropous  kind 
may  be  attached  in  such  a  way  as  to  bring  it  back,  by  a 
double  inversion,  to  the  upright  position.  The  castor  bean 
furnishes  a  good  example  of  this. 

133.  Seed  Dispersal. — This   subject  has  already  been 
touched  upon  in  the  chapter  on  fruits,  and  the  object  of 
distribution  is  in  both  cases  the  same.     The  agencies  of 
dispersal  are  either  natural,  i.e.  by  wind,  water,  and  animals, 
or  artificial,  that  is,  by  man. 

134.  Wind  Dispersal.  —  A  common  example  of  wind  dis- 
persal is  afforded  by  the  class  of  plants  known  to  farmers 
as  "  tumble  weeds."    Well-known  examples  of  these  are  the 
Russian  thistle,  winged  pigweed,  "  old  witch  grass,"  hair 


FORMS  AND  GROWTH  OF  SEED 


IOI 


grass,  etc.     Such  plants  generally  grow  in  light  soils  and 
either  have  very  light   root  sys- 
tems, or  are  easily  broken  from 


232.  —  Panicle  of  "  old  witch 
grass,"  a  common  tumble 
weed. 


231.  —  A  fruiting  plant  of  winged  pigweed 
(Cycloloma),  showing  the  bunchy  top  and  weak 
anchorage  of  a  typical  tumble  weed. 


their  anchorage  and  left  to  drift 
about  on  the  ground.  The 
spreading,  bushy  tops  become 
very  light  after  fruiting  so  as  to  be  easily  blown  about  by 
the  wind,  dropping  their  seeds  as  they  go,  until  they  finally 
get  stranded  in  ditches  and  fence  corners,  where  they 
often  accumulate  in  great  numbers  during  the  autumn 
and  winter. 

In  the  Japan  varnish  tree  {Sterculia  platanifolia)  the 
seeds  remain  attached  all  through  the  winter  to  the  open 
follicle,  which  becomes  very  light  when  dry,  and  acts  as  a 
sort  of  float  for  wafting  the  seeds  away  on  every  breeze. 

135.  Explosive  Capsules. — Some  plants  undertake  to 
disperse  their  seeds  without  the  intervention  of  any  external 


233  234  235 

233-235.  —  233,  A  pod  of  wild  vetch,  with  mature  valves  twisting  spirally  to 
discharge  the  seed ;  234,  pod  of  crane's-bill  discharging  its  seed ;  235,  capsules  of 
witch-hazel  exploding. 


,02  SEEDS   AND    SEEDLINGS 

agent.  Examples  of  this  kind  are  the  violet,  witch-hazel, 
and  touch-me-not,  whose  capsules  dehisce  with  a  little 
explosion  and  shoot  out  the  seeds  as  if  they  were  fairy 
mortars.  It  is  worth  while  to  gather  a  bough  of  witch-hazel 
in  winter  and  keep  it  in  the  schoolroom  to  watch  the  explo- 
sions. In  other  cases,  the  carpels  curl  upwards  with  a 
sudden  jerk,  as  in  some  of  the  geranium  family,  or  twist 
themselves  into  a  spiral,  like  the  valves  of  the  rabbit  pea 
(Vicia  americana),  thus  acting  as  a  spring  to  eject  the 
seeds. 

136.  Animal  Agency.  —  Examples  of  adaptation  for  dis- 
persal by  means  of  animals  were  given  in  Section  117,  but 
by  far  the  most  active  agent  in  the  dissemination  of  both 
fruits  and  seeds  is  man.  This  is  the  frequent  result  of 
intention  on  his  part,  in  the  introduction  and  cultivation  of 
new  grains,  fruits,  and  vegetables,  and  he  works  to  the  same 
end  unconsciously  and  often  to  his  great  detriment  by  the 
transportation  of  the  bulbs  or  seeds  of  pernicious  weeds  in 
the  dirt  clinging  to  hoes  and  plowshares,  and  the  mixture 
of  impurities  with  his  crop  seeds  through  ignorance,  care- 
lessness, or  unavoidable  causes.  This  mode  of  dispersal, 
however,  is  purely  artificial,  and  except  in  the  case  of  a 
few  weeds  that  have  adjusted  themselves  to  the  conditions 
of  cultivation,  is  not  correlated  with  any  special  adaptations 
in  the  plants  themselves,  many  of  our  most  widely  distrib- 
uted weeds,  such  as  the  rib  grass,  or  common  plantain,  the 
mayweed  and  the  narrow-leaved  sneezeweed,  possessing 
very  imperfect  natural  means  of  dispersal. 

PRACTICAL  QUESTIONS 

1.  Name  the  ten  most  troublesome  weeds  of  your  neighborhood. 

2.  What  natural  means  of  dispersal  have  they? 

3.  Which  of  them  seem  to  owe  their  propagation  to  man? 

4.  Are  there  any  tumble  weeds  in  your  neighborhood? 

5.  Should  you  expect  to  find  such  weeds  abundant  in  a  hilly  or  a 
very  woody  country? 

6.  What  situations  are  best  fitted  for  their  propagation? 

7.  Make  a  list  of  all  the  seeds  you  can  think  of  that  are  adapted  to 
dispersion  by  the  wind ;  by  water ;  by  animals. 


GERMINATION  103 

8.  Mention  some  of  the  ways  in  which  weeds  can  be  propagated 
by  careless  farmers. 

9.  Why  are  so  many  strange  weeds  or  other  new  plants  found  first 
along  railroad  tracks  ? 

10.  Account  for  the  absence  of  weeds  in  forests  and  groves. 

11.  Suggest  ways  for  checking  the  propagation  of  weeds,  and  of 
stopping  their  introduction. 

GERMINATION 

MATERIAL.  —  Seed  of  any  kind  that  will  germinate  readily  and  with 
a  moderate  degree  of  heat.  Corn,  oats,  cotton,  beans,  mustard,  will 
any  of  them  answer.  Six  or  eight  ordinary  preserving  jars,  or  bottles. 
Some  moist  cotton,  sawdust,  or  layers  of  blotting  paper,  or  old  flannel. 
Some  vaseline,  or,  if  this  is  not  at  hand,  lard. 

137.  Conditions  of  Germination.  —  If  kept  perfectly  dry, 
seed  may   sometimes  be  preserved  for  months,  or  even 
years.     Peas  have  been  known  to  sprout  after  ten  years, 
red  clover  after  twelve,  and  tobacco  after  twenty.     Ordi- 
narily, however,  the  vitality  of  seeds  diminishes  with  age, 
and  in  making  experiments  it  is  best  to  select  fresh  ones. 
The  ones  used  for  comparison  should  also,  as  far  as  pos- 
sible, be  of  the  same  size  and  weight. 

138.  Moisture.  —  Can  seeds  have  too  much  moisture  ? 
To  answer  this  question  drop  a  number  of  dry  grains  of 
corn,  oats,  or  other  convenient  seed,  into  a  bottle  or  other 
vessel  with  a  bedding  of  cotton  or  paper  that  is  barely 
moistened,  and  an  equal  number  of  soaked  seeds  of  the  same 
kind  into  another  vessel  with  a  saturated  bedding  of  the 
same  material.     In  a  third  vessel  place  the  same  number 
of  soaked  seed,  covering  them  partially  with  water,  and  in 
a  fourth  cover  the  same  number  entirely.      Label  them  I, 
2,  3,  and  4,  and  keep  all  together  in  a  warm  and  even 
temperature,  and  note  the  rate  of  germination  in  the  dif- 
ferent vessels. 

139.  Air.  —  Next  arrange  in  a  similar  manner  a  glass 
jar  containing  the  same  kind  of  seed  as  before,  using  a 
sufficient  quantity  to  fill  it  at  least  half  full.     The  vessel 
should  be  large  enough  to  hold  at  least  a  liter  (about  one 
quart).     Seal  it  hermetically  so  as  to  prevent  the  access  of 


104 


SEEDS   AND   SEEDLINGS 


fresh  air.  Label  it  5,  and  place  it  with  the  other  four.  The 
water  used  for  soaking  the  seeds  and  for  moistening  the 
bedding  in  this  experiment  should  first  have  had  its  con- 
tained air  expelled  by  boiling. 

To  test  the  behavior  of  seeds  in  the  entire  absence  of 
air  is  difficult,  because  it  is  not  possible  to  expel  all  traces 
of  the  atmosphere  even  with  an  air  pump. 

140.  Temperature.  —  Arrange  some  soaked  seeds  in 
three  or  four  different  vessels  just  as  in  No.  2,  in  the  first 
experiment,  and  place  where  they  will  be  subjected  to  dif- 
ferent temperatures,  ranging  say  from  o°  to  30°  C.  (about 
32°  to  86°  F.).  Test  frequently  with  a  thermometer,  keep- 
ing the  temperature  as  even  as  possible,  and  maintaining 
an  equal  quantity  of  moisture  in  each  vessel.  Keep  a 
record  of  the  number  of  seed  sprouted  in  each  after  every 
twenty-four  hours.  In  those  parts  of  the  South  where 
the  cold  is  not  continuous  enough  to  keep  seed  from  ger- 
minating under  ordinary  conditions,  experiments  in  low 
temperatures  can  not  very  well  be  made  unless  there  is  a 
refrigerator  available.  In  sections  where  there  is  continu- 
ous cold,  tests  might  also  be  made  of  the  minimum  tem- 
perature at  which  different  seeds  will  germinate.  Sachs 
found  the  minimum  for  corn  to  be  9°.4  C.  (about  49°  F.), 
and  for  the  gourd,  14°  C.  (about  58°  F.). 

141.    Recording  Observations.  —  Arrange  a  page  of  your 
notebook  after  the  model  given  below,  and  record  your 

NUMBER  OF  SEEDS  GERMINATED 


No.  of  hours      .     . 

24 

48 

72 

4d. 

5d. 

6d. 

7d. 

8d. 

rod. 

W2. 

No.  of  vessel     .     . 

I 

No.  of  vessel     .     . 

2 













No.  of  vessel     .     . 

3 









No.  of  vessel 

4 









No.  of  vessel 

5 









No.  of  vessel     .     . 

6 

GERMINATION  IO5 

observations  at  intervals  of  twenty-four  hours.  When 
most  of  the  seeds  in  jar  5  (Sec.  139)  have  begun  to  sprout, 
insert  a  thermometer  and  let  it  remain  two  or  three  min- 
utes. Does  it  indicate  any  change  of  temperature  ?  Re- 
fer to  Section  29  and  account  for  the  change.  If  cotton 
seed  are  used,  the  rise  of  temperature  will  be  very  marked. 

142.  Vitality.  —  A  very  interesting  point  is  to  test  the 
temperature  at  which  different  seed  lose  their  vitality,  by 
subjecting  dry  and  soaked  ones  of  various  kinds  to  dif- 
ferent degrees  of  heat  and  cold.     Notice  how  the  extremes 
tolerated  are  affected  by:  first,  the  length  of  time  the  seeds 
are  exposed ;  second,  by  the  amount  of  water  contained  in 
them ;  and  third,  by  the  nature  of  the  seed  coats.     Every 
farmer  knows  that  the  effect  of  freezing  is  much  more 
injurious  to  plants  or  parts   of  plants  when  full  of  sap 
(water)  than  when  dry.     This  is  because  in  freezing  the 
water  expands  and  ruptures  the  tissues,  thus  setting  up 
internal  disturbances  which  are  liable  to  result  in  death, 
especially  if  thawing  takes  place  so  rapidly  that  the  life 
processes  have  not  time  to  readjust  themselves.     In  like 
manner  it  will  be  found  that  when  seeds  are  subjected  to 
moist  heat,  they  are  killed  at  a  lower  temperature  and  in 
a  shorter  time  than  when  dry.     When   heated  in  water 
of  the  same  temperature,  those  seeds  will  be  found  to 
resist    best   whose    coats    are    most    impervious    to    the 
liquid. 

143.  Time  Required  for  Germination.  —  Arrange  in  a  bed 
of  moist  sand,  placed  between  two  soup  plates,  seeds  of 
various  kinds.     Good  specimens  would  be  some  of  the  fol- 
lowing :    corn,  wheat,    peas,    cotton,    okra,   turnip,   apple, 
morning-glory,  orange,  grape,  persimmon,  castor  bean,  pea- 
nut, etc.     Clip  some  of  the  harder  ones  and  place  them  in 
the  same  germinator  with  undipped  ones.     Keep  all  under 
similar  conditions  as  to  temperature,  moisture,  etc.,  and 
record  the  time  required  for  each  to  sprout.     What  is  the 
effect  of  clipping,  and  why  ? 


io6 


SEEDS   AND   SEEDLINGS 


144.   The  Relative  Value  of  Perfect  and  Inferior  Seed.  — 
From  a  number  of  seeds  of  the  same  species  select  half  a 


236.  —  Stem  development  of  seed-  237.  —  Stem  development  of  seedlings 

lings  raised  from   healthy  grains  of  raised  under  exactly  similar  conditions 

barley;    weight,  39.5   grams   (about  from  the  same  number  of  inferior  grains; 

500  grs.).  weight,  23  grams  (about  350  grs.). 

dozen  of  the  largest,  heaviest,  and  most  perfect,  and  an 
equal  number  of  small,  inferior  ones.  If  a  pair  of  scales 
is  at  hand,  the  different  sets  should  be  weighed  and  a 

record  kept  for 
comparison  with 
the  seedlings  at 
the  end  of  the  ex- 
periment. Plant 
the  two  sets  in 
pots  containing 
exactly  the  same 
kind  of  soil,  and 
keep  under  identi- 
238  239  cal  conditions  as 

238.  239-  —  Improvement  of  corn  by  selection:  238,  to  light  tempera- 
original  type;  239,  improved  type  developed  from  it. 

ture,  and  moisture. 

Keep  the  seedlings  under  observation  for  two  or  three 
weeks,  making  daily  observations  and  occasional  drawings 
of  the  height  and  size  of  the  stems,  and  the  number  of 
leaves  produced  by  each. 

These  experiments  can   be  carried  on   simultaneously 
with   the    study   of    Seedlings    and    Growth.      It    is    not 


SEEDLINGS  IO? 

expected  that  any  one  class  will  have  time  to  complete 
them  all,  but  a  number  are  suggested  in  order  that  dif- 
ferent teachers  may  choose  the  ones  best  suited  to  their 
circumstances. 

PRACTICAL  QUESTIONS 

1.  What  are  the  principal  external  conditions   that  affect  germi- 
nation ?     (137,138,139,140.) 

2.  What  effect  has  cold?     Want  of  air?    Too  much  water? 

3.  Is  light  necessary  to  germination? 

4.  What  is  the  use  of  clipping  seeds  ? 

5.  In  what  cases  should  it  be  resorted  to? 

6.  Why  will  seed  not  germinate  in  hard,  sun-baked  land  without 
abundant  tillage  ?     Why  not  on  undrained  or  badly  drained  land  ? 
(133,  I39-) 

7.  Will  seeds  that  have  lost  their  vitality  swell  when  soaked? 

8.  Are  there  any  grounds  for  the  statement  that  the  seeds  of  plums 
boiled  into  jam  have  sometimes  been  known  to  germinate  ? l     (142.) 

9.  Could  such  a  thing  happen  in  the  case  of  apples  or  watermelons, 
and  why  or  why  not  ?     (142.) 

10.  Does  it  make  any  difference  in  the  health  and  vigor  of  a  plant 
whether  it  is  grown  from  a  large  and  well-developed  seed  or  from  a 
weak  and  puny  one  ?     (144.) 

1 1 .  Would  a  farmer  be  wise  who  should  market  all  his  best  grain 
and  keep  only  the  inferior  for  seed  ? 

12.  What  would  be  the  result  of  repeated  plantings  from  the  worst 
seed? 

13.  Of  constantly  replanting  the  best  and  most  vigorous? 

SEEDLINGS 

MATERIAL.  —  Seedlings  of  various  kinds  in  different  stages  of 
growth.  Those  from  seeds  experimented  with  in  Sections  137-144  may 
be  used  to  begin  with.  Corn,  oats,  bean,  squash,  cotton,  are  the  ones 
mentioned  in  the  text.  Ash,  maple,  morning-glory,  or  castor  bean 
may  be  used  instead  of  cotton,  but  the  last  two  are  rather  difficult 
to  germinate,  requiring  from  8  to  10  days,  or  even  longer,  if  the 
temperature  is  too  low.  Soaked  seeds  of  cotton  and  corn  will  ger- 
minate in  from  3  to  7  days,  according  to  the  temperature;  oats  in 
I  to  4,  beans  in  4  to  6,  squash  in  8  to  10.  Germination  will  be 
greatly  facilitated  by  soaking  the  seeds  for  12  to  24  hours  before  plant- 
ing them,  and  very  obdurate  ones  may  be  forced  by  clipping. 

1  Vines,  "  Lectures  on  the  Physiology  of  Plants,"  p.  282.  See  also,  Sachs, 
"  Physiology  of  Plants." 


I08  SEEDS   AND   SEEDLINGS 

A  good  germinator  can  be  made  by  putting  moist  sand  or  sawdust 
between  two  plates.  The  germinator  should  be  kept  at  an  even  tem- 
perature of  about  20°  C.  (70°  F.).  Seeds  even  of  the  same  kind  develop 
at  such  different  rates  that  it  will  probably  not  be  necessary  to  make 
more  than  two  plantings  of  each  sort,  about  4  or  5  days  apart.  Enough 
must  be  provided  to  give  each  pupil  3  or  4  specimens  in  different 
stages  of  development. 

145.  Seedlings  of  Monocotyledons.  —  Examine  a  grain  of 
corn  that  has  just  begun  to  sprout;  from  which  side  does 

240  the  seedling  spring,  the  plain  or  the 
grooved  one  ?  Refer  to  your  sketch  of 
the  dry  grain  and  see  if  this  agrees  with 
the  position  of  the  embryo  as  observed 
in  the  seed.  Make  sketches  of  four  or 
five  seedlings  in  different  stages  of 
advancement,  until  you  reach  one  with 
a  well-developed  blade.  Examine  each 
carefully  with  regard  to  the  cotyledon, 
the  root,  and  the  plumule.  Which  part 
first  appeared  above  the  ground  ?  In 
what  direction  does  the  plumule  grow? 
The  hypocotyl?  Does  the  cotyledon 
240.  241.  —  Seedling  appear  above  ground  at  all?  Slip  off 

z^a^stag^of   the  seed  coats  and  see  if  there  is  any 
germination;  241,  later    difference   in  the  size  and  appearance 

of  the  contents  as  you  proceed  from 
the  younger  to  the  older  plants.  How  would  you  account 
for  the  difference  ? 

146.  The  Cotyledon. — Is  the  cotyledon  of  any  use  to  the 
seedling  when   it  remains  in   the  ground  ?     In  order  to 
answer  this  question,  cut  away  carefully,  so  as  not  to  injure 
the  plumule,  the   cotyledon  with  its   endosperm,  from  a 
very  young  seedling,  and  place  on  a  piece  of  coarse  netting 
stretched  over  a  glass  of  water  so  that  its  roots  will  touch 
the  liquid.     Put  beside  it  another  seedling  of  the  same  age 
and  size  from  which  the  cotyledon  has  not  been  removed, 
and  watch  their  growth  for  a  week  or  ten  days.     Which 
has  developed  most  rapidly  in  that  time  ?     Test  the  coty- 


SEEDLINGS 


109 


ledon  on  the  second  seedling  for  starch ;  what  has  become 
of  it?  Test  sections  of  the  root  and  stem  of  the  same 
seedling  and  see  if  any  of  the  starch  has  gone  into 
them. 

147.  Growth  of  the  Plumule.  —  What  part  of  the  plumule 
comes  out  of  the  ground  first  ?     Is   it  straight   or  bent  ? 
Open  the  outer  sheath  of  a  well-developed  plumule  with  a 
needle ;  what  do  you  find  inside  ?     Examine  the  plumule 
of  an  older  plant  that  has  developed  several  leaves ;  where 
does  the  second  one  come  from  ?     Look  within  that  for 
the  next  one  ;  from  where  does  the  new  leaf  always  seem 
to  proceed?      Measure  the  internodes  from  day  to  day 
and  note  their  rate  of  growth  in  your  book. 

148.  Growth  of  the  Root.  —  Examine  the  lower  end  of 
the  hypocotyl  and  find  where  the  roots  originate.     Ob- 
serve their  tendency  to  spread  out  in 

every  direction,  and  even  to  develop 
from  the  lower  nodes  of  the  hypo- 
cotyl ;  would  you  say  that  the  roots 
are  an  outgrowth  from  the  stem,  or 
the  stem  from  the  root?  Mark  off 
a  root  into  sections  by  moistening  a 
piece  of  sewing  thread  with  indelible 
ink  and  applying  it  to  the  surface 
of  the  root  at  intervals  of  about  one 
millimeter  (^  of  an  inch).  Lay  the 
seedling  on  a  moist  bedding  in  a  glass 
jar,  covered  lightly  to  prevent  evap- 
oration, and  watch  to  see  in  what  part 
of  the  root  growth  takes  place. 

Notice  the  grains  of  sand  or  saw-   "T^tV"^ 

dust     that     Cling     tO     the     rootlets     Of     stage  of  germination ;  243, 

plants   grown  in  a  bedding   of   that    laterstage- 
kind.     Examine  with  a  lens  and  see  if  you  can  account  for 
their  presence.     Lay  the  root  in  water  on  a  bit  of  glass, 
hold  up  to  the  light  and  look  for  root  hairs  ;  on  what  part 
are  they  most  abundant? 


242,  243. 


—  Seedli 


ng  of 


no 


SEEDS   AND   SEEDLINGS 


149.  Root  Hairs  are  the  chief  agents  in  absorbing  mois- 
ture from  the  soil.     They  do  not  last  very  long,  but  are 

constantly  dying  and  being  formed  again  in 
the  younger  and  tenderer  parts  of  the  root. 
These  are  usually  broken  away  in  tearing 
the  roots  from  the  soil,  so  that  it  is  not 
easy  to  detect  them  except  in  seedlings,  even 
with  a  microscope.  In  oat  and  maple  seed- 
lings they  are  very  abundant  and  clearly 
visible  to  the  naked  eye.  The  amount  of 
absorbing  surface  on  a  root  is  greatly  in- 
—  Seediin  creased  by  the  presence  of  the  hairs ;  and 

of  wheat,  with  they  exude,  moreover,  a  slightly  acid  secre- 
tion, which  aids  them  in  dissolving  and 

absorbing  the  mineral  substances  contained  in  the  particles 

of  earth  and  sand  to  which  they  adhere. 

150.  The  Root  Cap.  —  Look  at  the  tip  of  the  root  through 
your  lens  and  notice  the  soft,  transparent, 

crescent  or  horseshoe-shaped  mass  in  which 
it  terminates.  This  is  the  root  cap  and 
serves  to  protect  the  tender  parts  behind 
it  as  the  roots  burrow  their  way  through 
the  soil.  Being  soft  and  yielding,  it  is  not 
so  likely  to  be  injured  by  the  hard  sub- 
stances with  which  it  comes  in  contact  as 
the  more  compact  tissue  of  the  roots.  It 
is  composed  of  the  loose  cells  out  of  which 
the  solid  root  substance  is  being  formed, 
and  the  growing  point  of  the  root  is  at  the 
extremity  of  the  tip  just  behind  the  cap 
(Fig.  245).  The  cap  is  very  apparent  in 
a  seedling  of  corn,  and  can  easily  be  seen 
with  the  naked  eye,  especially  if  a  thin 
longitudinal  section  is  made.  It  is  also 
well  seen  in  the  water  roots  of  the  common  c>  root  caP:  £• 
duckweed  (Lemna\  and  on  those  developed  gr°wing  P°im' 
by  a  cutting  of  the  wandering  Jew,  when  placed  in  water. 
Are  there  any  hairs  on  the  root  cap? 


SEEDLINGS 


III 


A  good  way  to  study  the  small,  delicate  parts  of  plants 
is  to  place  them  between  two  thin,  clear  pieces  of  glass  and 
hold  up  to  the  light.  Even  without  a  lens  many  peculiari- 
ties of  structure  can  in  this  way  be  made  apparent  to  the 
eye. 

Instead  of  corn,  seedlings  of  wheat  or  oats  may  be  used, 
and  if  time  permits  it  would  be  well  to  examine  and  com- 
pare the  two. 

151.  Organs  of  Vegetation.  —  These  three  organs,  root, 
stem,  and  leaf,  are  all  that  are  necessary  to  the  individual 
life  of  the  plant.  They  are  called  organs  of  vegetation 
in  contradistinction  to  the  flower  and  fruit,  which  consti- 
tute the  organs  of  reproduction.  The  former  serve  to 
maintain  the  plant's  individual  existence, 
the  latter  to  produce  seed  for  the  propa- 
gation of  the  species,  so  we  find  that  the 
seed  is  both  the  beginning  and  the  end  of 
vegetable  life. 


152.  Poly-cotyledons.  —  The  pine  is  very 
difficult  to  germinate,  requiring  usually 
from  1 8  to  21  days,  but  if  a  seedling  can 
be  obtained  it  will  make  an  interesting 
study.  By  soaking  the  mast  for  24  hours 
and  planting  in  damp  sand  kept  at  an  even 
temperature  of  not  less  than  23°  C.  (74°  or 
75°  F.)  a  few  specimens  may  be  obtained. 


246.  —  Seedling    of 
pine  (GRAY). 


153.  Seedlings  of  Dicotyledons.  —  Sketch,  without  remov- 
ing it,  a  bean  seedling  that  has  just  begun  to  show  itself 
above  ground ;  what  part  is  it  that  protrudes  first  ?  Sketch 
in  succession  four  or  five  others  in  different  stages  of 
advancement.  Notice  how  the  hypocotyl  is  arched  where 
it  breaks  through  the  soil.  Can  you  account  for  this? 
Does  it  occur  in  the  monocotyledons  examined  ?  Almost 
all  dicotyledons  exhibit  this  peculiarity  in  germination ; 
can  you  see  what  causes  it?  Do  the  cotyledons  appear 
above  ground  ?  How  do  they  get  out  ?  Can  you  perceive 


112 


SEEDS   AND    SEEDLINGS 


any  advantage  in  their  being  dragged  out  of  the  ground 
backwards  in  this  way  rather  than 
pushed  up  tip  foremost  ?  What 
changes  have  the  cotyledons  under- 
gone in  the  successive  seedlings  ? 
Remove  from  the  earth  a  seedling 
just  beginning  to  sprout  and  sketch 
it.  From  what  point  does  the  hypo- 
cotyl  protrude  through  the  coats  ? 
Does  this  agree  with  its  position  as 
sketched  in  your  study  of  the  seed  ? 
In  which  part  of  the  embryo  does 
the  first  growth  seem  to  have  taken 
place  ? 

Remove  in  succession  the  several 


247.  —  Seedlings  of  bean  in 
different  stages  of  growth :  c c, 
cotyledons,  showing  the  plu- 
mule and  hypocotyl  before 
germination ;  a,  b,  d,  and  e, 
successive  stages  of  advance-  seedlingS  yOU  have  sketched  and 

note  their  changes.  How  does  the 
root  differ  from  that  of  the  corn 
and  oats  ?  Look  for  root  hairs ;  if 
there  are  any,  where  do  they  occur  ?  Mark  off  the  root  of  a 
young  seedling  into  sections  as  directed  in  Section  148,  and 


ment.  At  d  the  arch  of  the 
hypocotyl  is  beginning  to 
straighten ;  at  e  it  has  entirely 
erected  itself. 


248,  249.  —  Root  of  bean  seedling, 
measured  to  show  region  of  growth : 
248,  early  stage  of  germination;  249, 
later  stage. 


250  251 

250,  251.  —  Stem  of  bean  seedling, 
measured  to  show  region  of  growth: 
250,  early  stage  of  growth ;  251,  later 
stage. 


SEEDLINGS  1 1 3 

watch  it  from  day  to  day.  In  what  part  does  growth  take 
place  ?  Mark  off  a  node  of  the  stem  in  a  similar  manner 
and  find  out  how  it  grows.  Allow  a  seedling  to  develop 
until  it  has  put  forth  several  leaves,  and  measure  daily  the 
successive  internodes.  Does  an  internode  stop  growing 
when  the  one  next  above  it  has  formed  ?  When  is  growth 
most  rapid  ?  Reverse  the  position  of  a  number  of  seed- 
lings that  have  just  begun  to  sprout  and  watch  what  will 
happen.  A  good  way  to  observe  the  growth  of  roots  is  to 
fill  a  glass  jar  or  a  lamp  chimney  with  moist  cotton  or  saw- 
dust, and  insert  the  seedling  between  the  side  of  the  jar 
and  the  moist  filling. 

154.  Cotton.  —  Examine  a  number  of  cotton  seedlings 
in  different  stages  of  growth.  What  part  appears  above 
ground  first?  How  does  this  compare  with  the  first  ap- 
pearance of  the  bean  ?  Of  corn  and  oats  ?  Pull  up  a  seed- 
ling that  has  just  begun  to  sprout ;  does  the  root  come 
from  the  big  or  the  little  end  of  the  seed  ?  Does  this  agree 
with  what  you  learned  about  the  position  of  the  hypocotyl 
in  Sections  121  and  122?  Notice  how  the  coats  adhere 
at  the  chalaza,  even  after  the  cotyledons  are  well  above 
ground  ;  is  this  woolly  nightcap  of  any  special  service  to 
a  delicate  plant  like  the  cotton  ?  Notice  the  little  speckled 
glands  that  cover  the  stem  and  the  cotyledons.  What 
change  of  color  do  the  latter  undergo  as  the  seedling  de- 
velops ?  How  do  they  compare  as  foliage  leaves  with 
those  of  the  bean,  squash,  etc.  ?  With  the  foliage  leaves 
of  the  mature  cotton  plant  ?  Of  what  use  to  a  plant  are 
the  cotyledons  when  they  appear  above  ground  ?  To 
answer  this  question  cut  away  the  cotyledons  from  a 
number  of  seedlings  as  soon  as  they  appear,  and  ob- 
serve the  result  as  compared  with  others  that  have  not 
been  cut. 

Pull  up  a  seedling  and  sketch  it  entire,  showing  the 
long,  straight  taproot.  How  does  it  compare  in  length 
with  that  of  the  bean  ?  How  do  both  differ  from  those  of 
the  corn  and  oats  ?  Measure  the  growth  of  the  root  and 

ANDREWS'S    HOT.  —  8 


II4  SEEDS  AND   SEEDLINGS 

stem  as  you  did  in  the  bean.  Reverse  the  position  of  a 
number  of  seedlings,  so  that  the  hypocotyl  shall  point 
upward  and  the  plumule  downward,  and  watch  the  effect 
upon  their  growth.  After  a  few  days  reverse  them  again 
and  note  the  effect.  In  sections  where  cotton  seed  can  not 
be  obtained,  maple,  ash,  morning-glory,  or  squash,  pumpkin, 
etc.,  may  be  substituted. 


PRACTICAL  QUESTIONS 

1 .  Do  the  cotyledons,  as  a  general  thing,  resemble  the  mature  leaves 
of  the  same  plants? 

2.  Try  to  account  for  the  difference,  if  you  observe  any ;  could  con- 
venience of  packing  in  the  seed  coats,  for  instance,  have  anything  to 
do  with  it? 

3.  If  seeds  are  planted  in  the  ground  in  a  number  of  different  posi- 
tions, will  there  be  any  difference  in  the  position  of  the  seedlings  as 
they  appear  above  ground? 

4.  Of  what  advantage  to  the  farmer  is  this  tendency  of  seedlings  to 
right  themselves? 

GROWTH 

MATERIAL.  —  A  flower  pot  suspended  by  a  wire,  some  bulbs,  and 
several  well-developed  seedlings  to  experiment  with. 

155.  What  Growth  Is. — With  the  seedling  begins  the 
growth  of  the  plant.  Most  people  understand  by  this 
word,  mere  increase  in  size  ;  but  growth  is  something  more 
than  this.  It  involves  a  change  of  form,  usually,  but  not 
necessarily,  accompanied  by  increase  in  bulk.  Mere  me- 
chanical change  is  not  growth,  as  when  we  bend  or  stretch 
an  organ  by  force,  though  if  it  can  be  kept  in  the  altered 
position  till  such  position  becomes  permanent,  or  as  we  say 
in  common  speech,  "  till  it  grows  that  way,"  the  change 
may  become  growth.  To  constitute  true  growth,  the 
change  of  form  must  be  permanent,  and  brought  about, 
or  maintained  by  forces  within  the  plant  itself. 

Remove  the  scales  from  a  white-lily  bulb,  weigh  them,  and 
lay  them  in  a  warm,  not  too  damp,  place,  away  from  light. 


GROWTH  115 

After  a  time  young  bulblets  will  form  at  the  base  of  each 
scale.  Weigh  the  scales  again,  and  if  there  has  been  any 
loss,  account  for  it  (see  Sections  24-27,  and  65).  The 
same  experiment  can  be  tried  by  allowing  hyacinth  or 
other  bulbs  to  germinate  without  absorbing  moisture 
enough  to  affect  their  weight. 

156.  Conditions  of  Growth.  —  The   internal   conditions 
depend  upon  the  organization  of  the  plant.     The  essential 
external  conditions  are :  food  material,  water,  oxygen,  and 
a  sufficient  degree  of  warmth.     It  may  be  greatly  influ- 
enced by  other  circumstances,  such  as  light,  gravitation, 
pressure,    and   (probably)   electricity,    but   the    four   first 
named    are   the   essential   conditions    without   which   no 
growth  is  possible. 

157.  Region  of  Growth.  —  It  was  seen  in  Sections  148 
and  153  that  the  region  of  active  growth  in  the  root  is 
just   above  the  tip,  behind   the  cap.      In   the   stem  the 
region  of  increase  is  more  evenly  distributed,  the  lower 
nodes  continuing  to  grow  for  some  time  after  the  others 
are  formed,  but  a  little  observation  will  show  that  in  stems 
also,  growth  is  usually  most  active  in  the  region  near  the 
apex,  where  new  cells  are  being  produced. 

158.  Cycle  of  Growth.  —  When  an  organ  becomes  rigid 
and  its  form  fixed,  there  is  no  further  growth,  but  only 
nutrition  and   repair,  processes  which  must  not   be   con- 
founded with  it.     Every  plant  and  part  of  a  plant  has  its 
period  of  beginning,  maximum,  decline,  and  cessation  of 
growth.     The  cycle  may  extend  over  a  few  hours,  as  in 
some  of  the  fungi,  or,  in  the  case  of  large  trees,  over  thou- 
sands of  years. 

159.  Direction  of  Growth.  —  Plant  in  a  pot  suspended  as 
shown  in  Figure  252,  a  healthy  seedling  of  some  kind,  two 
or  three  inches  high,  so  that  the  plumule  shall  point  down- 
ward through  the  drain  hole  and  the  root  upward  into  the 
soil.     Watch  the  action  of  the  stem  for  six  or  eight  days, 


u6 


SEEDS   AND   SEEDLINGS 


and  sketch  it.  After  the  stem  has  directed  itself  well  up- 
ward, invert  the  pot  again, 
and  watch  the  growth. 
After  a  week  remove  the 
plant  and  notice  the  direc- 
tion of  the  root.  Sketch  it 
entire,  showing  the  changes 
of  direction. 

At  the  same  time  that 
this  experiment  is  arranged, 
lay  another  pot  with  a 
rapidly  growing  plant  on 
one  side,  and  every  forty- 
eight  hours  reverse  the 

252,   253.  —  Experiment  showing  the     position    of    the    pot,    laying 

^-."S^^Z!    it  on  the  opposite  side.     At 

253,  the  same  after  an  interval  of  eight     £hQ    end    of    ten    Or    twelve 

days  remove  the  plant  and 

examine.     How  has  the  growth  of  root  and   stem  been 
affected  ? 

What  do  we  learn  from  these  experiments  and  from 
those  in  Sections  153  and  154,  as  to  the  normal  direction 
of  growth  in  these  two  organs  respectively  ? 

160.  Geotropism.  —  This  general  tendency  of  the  grow- 
ing axes  of  plants  to  take  an  upward  and  downward  course 
—  in  other  words  to  point  to  and  from  the  center  of  the 
earth  —  is    called    geotropism.     It    is    positive    when   the 
growing  organs  point  downwards,  as  most  primary  roots 
do ;  negative  when  they  point  upwards,  as  in  most  primary 
stems ;  and  transverse  or  lateral,  when  they  extend  hori- 
zontally,  as   is  the  case  with  most   secondary  roots    and 
branches. 

161.  Gravity  and  Growth. —  It  has  been  proved  by  ex- 
periment that  geotropism  is  due  to  gravity.     It  must  be 
carefully  noted,  however,  that  the  influence  here  alluded  to 
is  not  the  mere  mechanical  effect  of  gravity  due  to  weight 
of  parts,  as  when  the  bough  of  a  peach  or  an  orange  tree 


GROWTH 


117 


is  bent  under  the  load  of  its  fruit,  but  a  certain  stimulus  to 
which  the  plant  reacts  by  a  spontaneous  adjustment  of 
its  growing  parts.  In  other  words, 
geotropism  is  an  active  and  not  a 
passive  function,  and  the  plant  will 
even  overcome  considerable  resist- 
ance in  response  to  it.  If  a  sprouted 
bean  is  laid  on  a  dish  of  mercury 


254.  —  Experiment   sho\v- 
ng  the   root  of   a  seedling 


covered  with  a  layer  of  water,  as  in    f°rcin«  its  way  downward 

*  through  mercury. 

Figure  254,  the  root  will  force  its  way 

downward  into  the  liquid,  although  the  mercury  is  fourteen 
times  heavier  than  an  equal  bulk  of  the  bean  root  substance, 
and  the  geotropism  of  the  root  must  thus  overcome  a  resist 
ance  equal  to  at  least  fourteen  times  its  own  weight. 

162.    Other  Factors.  — The  direction  of  growth  is  influ- 
enced by  many  other  factors,  such  as  light,  heat,  contact 


255. —A  piece  of  a  haulm  of  millet  that  has  been  laid  horizontally,  righting  itself 
through  the  combined  influence  of  contact  and  negative  geotropism. 

with  other  bodies,  and  perhaps  by  electricity.     The  result 
of  all  these  forces  is  an  endless  variety  in  the  forms  and 


n8  SEEDS   AND   SEEDLINGS 

direction  of  organs  that  seems  to  defy  all  law.  Heat,  un- 
less excessive,  generally  stimulates  growth ;  contact  some- 
times simulates  it,  causing  the  stem  to  curve  away  from  the 
disturbing  object,  and  sometimes  retards  it,  causing  the  stem 
to  curve  towards  the  object  of  contact  by  growing  more 
rapidly  on  the  opposite  side,  as  in  the  stems  of  twining 
vines.  Light  stimulates-  nutrition,  but  generally  retards 
growth.  The  heliotropic  movements  of  plants  (Sections 
54-57)  are  effected  in  this  way  ;  the  growth  being  checked 
on  that  side,  the  plant  bends  toward  the  light 

163.  Internal  Forces  of  the  Plant.  —  Another  important 
factor  exists  in  the  internal  constitution  of  the  plant  itself. 
Place  a  segment  of  prickly  pear  (Opuntia)  or  other  cactus, 
tip  downward  in  the  soil ;  roots  will  develop  with  great 
difficulty  :  because  the  natural  forces  of  the  plant  tend  to 
carry  the  root  forming  material  to  the  base,  and  it  takes 
time  for  the  external  factors  of  dampness,  moisture,  and 
gravitation  to  overcome  this  inherent  tendency.  Place  two 
leafy  twigs  of  some  herbaceous  plant,  one  in  its  natural 
position,  the  other  bottom  upwards,  in  a  vase  of  water, 
and  notice  the  difference  in  the  wilting  of  the  leaves,  due 
to  a  physiological  tendency  in  the  conducting  cells  to  carry 
the  crude  sap  toward  the  apex. 

PRACTICAL  QUESTIONS 

1.  Why  do  stems  of  corn,  wheat,  rye,  etc.,  straighten  themselves 
after  being  prostrated  by  the  wind  ?     (162.) 

2.  Can  a  plant  grow  and  lose  weight  at  the  same  time ?     (155.) 

3.  Do  plants  grow  most  rapidly  in  the  daytime,  or  at  night?    (162.) 
4.^  Reconcile  this  with  the  fact  that  green  plants  will  finally  die  if 

deprived  of  light. 

5.  Which  would  be  richer  in  nourishment,  hay  cut  in  the  evening  or 
in  the  morning  ?    Why  ?     (24,  25,  26,  162.) 

6.  Which  grows  more  rapidly,  a  young  shoot  or  an  old  one  ? 

7-  Which,  as  a  general  thing,  are  the  more  rapid  growers,  annuals 
or  perennials  ?  Herbaceous  or  woody-stemmed  plants  ? 

8.  Name  some  of  the  most  rapid  growers  you  know  ? 

9.  Of  what  advantage  is  this  habit  to  them  ? 

1  Sachs,  "  Physiology  of  Plants." 


GROWTH  1 19 


FIELD  WORK 

The  subjects  treated  in  this  chapter  can  best  be  studied  in  the 
laboratory,  and  afford  little  opportunity  for  field  work,  except  in  regard 
to  the  various  adaptations  for  the  protection  and  dispersal  of  seed. 
Look  through  the  woods  and  fields  for  examples  of  these  adaptations 
and  explain  how  they  are  each  suited  to  their  purpose.  To  an  imagina- 
tive mind  there  is  something  almost  pathetic  in  what  seem  to  be  the 
shifts  employed  by  the  mother  plants,  themselves  incapable  of  motion, 
to  launch  their  offspring  in  the  world. 

Note  the  absence  of  weeds  in  woodlands  and  places  remote  from 
cultivation,  and  account  for  it.  Look  along  railroads,  along  common 
roadsides,  around  wharves,  factories,  railroad  stations,  warehouses,  and 
barnyards,  for  introduced  plants,  and  account  for  their  presence.  Study 
the  history,  habits,  and  the  local  distribution  of  some  of  the  common 
weeds  of  your  neighborhood,  and  suggest  means  for  extirpating  them. 


V.     ROOTS   AND  UNDERGROUND  STEMS 

FUNCTION  AND  STRUCTURE  OF  ROOTS 

MATERIAL.  — Two  earthen  pots,  with  a  growing  plant  in  one.  Some 
coarse  netting,  a  common  tumbler,  and  sprouting  seeds  of  mustard,  or 
other  easily  germinating  kind.  A  stalk  with  roots,  of  corn  or  any  kind 
of  grass,  and  one  of  cotton  or  other  woody  plant.  A  woody  taproot 
inserted  in  red  ink  from  four  to  six  hours  before  the  lesson  begins. 

164.  Roots  as  Holdfasts.  —  One  use  of  ordinary  roots  is 
to  serve  as  props  and  stays  for  anchoring  plants  to  the  soil. 
Tall  herbs  and  shrubs,  and  vegetation  generally  that  is 


a  b 

256.  —  Dandelion :  a,  common  form,  grown  in  plains  region  at  low  altitude ; 
b,  alpine  form. 

exposed  to  much  stress  of  weather,  are  apt  to  have  large, 
strong  roots.  Even  plants  of  the  same  species  will  develop 
systems  of  very  different  strength  according  as  they  grow 
in  sheltered  or  exposed  places. 

165.  Root  Pull,  —  Roots  are  not  mere  passive  holdfasts, 
but  exert  an  active  downward  pull  upon  the  stem.  Notice 
the  rooting  end  of  a  strawberry  or  raspberry  shoot  and 
observe  how  the  stem  appears  to  be  drawn  into  the  ground 


FUNCTION  AND  STRUCTURE  OF  ROOTS 


121 


at  the  rooting  point.     In  the  leaf  rosettes  of  herbs  growing 
flat    on    the    ground    or    in    the 
crevices  of  walls  and  pavements, 
the  strong  depression  observable 
at  the  center  is  due  to  root  pull. 

166.  Roots  absorb  Moisture. — 
Fill  two  pots  with  damp  earth, 
put  a  healthy  plant  in  one  and  set 
them  side  by  side  in  the  shade. 
After  a  few  days  examine  by  dig- 
ging into  the  soil  with  a  fork  and 
see  in  which  pot  it  has  dried  most. 


Where   has   the   moisture 
how  did  it  get  out  ? 


gone 


167.  Roots  shun  the  Light. — 
Cover  the  top  of  a  glass  of  water 

with  thin  netting,  lay  On  it  Sprout-     257.  — Raspberry  stolon  showing 

ing  mustard  or  other  convenient 

seed.  Allow  the  roots  to  pass  through  the  netting  into 
the  water,  noting  the  position  of  root  and  stem.  Envelop 
the  sides  of  the  glass  in  heavy  wrapping  paper,  admitting 
a  little  ray  of  light  through  a  slit  in  one  side,  and  after  a 
few  days  again  observe  the  relative  position  of  the  two 
organs.  How  is  each  affected  by  the  light  ? 

168.  Roots  seek  Air.  —  Remove  a  plant  from  a  porous 
earthenware  pot  in  which  it  has  been  growing  for  some 
time  ;    the  roots  will  be  found  spread  out  in  contact  with 
the  walls  of  the  pot  instead  of  embedded  in  the  soil  at  the 
center.     Why  is  this  ? 

169.  Roots  seek  Water.  —  Stretch  some  coarse  netting 
covered  with   moist   batting   over   the   top   of   an  empty 
tumbler.     Lay  upon  it  some  seedlings,  as  in  Section  167, 
allowing  the  roots  to  pass  through  the  meshes  of  the  net- 
ting.    (A  piece  of  cardboard  with  holes  in  it  will  answer.) 
Keep  the  batting  moist,  but  take  care  not  to  let  any  of  the 
water  run  into  the  vessel.    Observe  the  position  of  the  roots 


122 


ROOTS    AND   UNDERGROUND    STEMS 


at  intervals,  for  twelve  to  twenty-four  hours,  then  fill  the 
glass  with  water  to  within  10  millimeters  (a  half  inch, 
nearly)  or  less  of  the  netting,  let  the  batting  dry,  and  after 
eight  or  ten  hours  again  observe  the  position  of  the  roots. 
What  would  you  infer  from  this  experiment  as  to  the  affin- 
ity of  roots  for  water  ? 

170.  Taproots.  —  Gather  a  stalk 
of  cotton  or  any  hard  wood  shrub,, 
and  one  of  corn  or  other  grain,  and 
compare  them  with  each  other  and 
with  the  roots  of  seedlings  of  the 
same  specie's.  Notice  the  differ- 
ence in  their  mode  of  growth.  In 
the  first  kind  a  single  stout  pro- 
longation called  a  taproot  proceeds 
from  the  lower  end  of  the  hypo- 
cotyl  and  continues  the  axis  of 
258.— Branched^  taproot  of  growth  straight  downwards,  unless 
turned  aside  by  some  external  influ- 
ence. A  taproot  may  be  either  simple,  as  in  the  turnip, 
radish,  dandelion,  and  most  herbs,  or  branched,  as  in 
shrubs  and  trees  generally.  In  this 
case  the  main  axis  is  called  the 
primary  root,  and  the  branches  are 
secondary  ones. 


259.  —  Fibrous  root. 


171.  Fibrous  and 
Fascicled  Roots.  — 
In  corn  and  other 
grasses  the  main 
axis  has  become 
aborted,  or  failed 

to  develop,  and  a  number  of  independent 
branches  spring  from  its  stub,  forming 
260. -Fascicled  and    wfcat  are  known  as  fibrous  roots  :  or  the 

tuberous    or    fusiform 

(secondary)  roots  of  base  of  the  hypocotyl,  instead  of  con- 
base1  of  the  stem^a/S"  tmuing  downward  in  a  single  axis,  may 
GRAY).  split  up  into  a  number  of  smaller  ones- 


FUNCTION  AND  STRUCTURE  OF  ROOTS 


123 


as  in  the  pumpkin.     When  roots  of  this  kind  are  thick  and 
fleshy,  they  are  usually  described  as  fascicled. 

172.  The  Two  Modes  of  Growth.  — This  difference  in  the 
mode  of  growth  is  very  apparent  in  the  seedling,  as  will 
be  evident  on  referring  to  your  sketches.     The  first  kind 
is  called  the  axial  mode,  because  it  is  a  continuation  of  the 
main  axis  of  the  plant ;  the  second  is  the  nonaxial,  or  for 
want  of  a  better  word  we  may  call  it  the  radial  mote,  since 
the  roots  radiate  in  all  directions  from  a  common  axis. 

173.  Importance  of  this  Distinction.  —  This  distinction 
has  important  bearings  in  agriculture.     Roots  of  the  first 
kind,  which  are  characteristic  of  most  dicotyledons,  strike 
deep,  and  draw  their  nourishment  from  the  lower  strata  of 
the  soil,  while  the  radial  kind  spread  out  near  the  surface 
and  are  more  dependent  upon  external  conditions. 

174.  Root  Structure.  —  Cut  a  cross  section  of  any  woody 
taproot  about  halfway  between   the  tip   and  the   ground 
level,  examine  it  with  a  lens  and  sketch  it.      Label  the 
dark  outer  covering,  epider- 
mis, the  soft  layer  just  within 

that,  cortex,  the  hard,  woody 
axis  that  you  find  in  the 
center,  vascular  cylinder,  and 
the  fine  silvery  lines  that 
radiate  from  the  center  to 
the  cortex,  medullary  rays 
(in  a  very  young  root,  these 
will  not  appear).  Cut  a  sec- 
tion through  a  root  that  has 
stood  in  red  ink  for  about 
three  hours  and  note  the 


261.  —  Cross  section  of  a  young  tap- 
root: a,  a,  root  hairs;  b,  epidermis;  c, 
cortical  layer;  d,  fibrovascular  cylinder. 


parts    colored    by    the    fluid.      Note  the  absence  of  medullary  rays  dur- 
'  ing  the  first  year  of  growth. 

What   portion  of   the   root, 

should   you  judge  from  this,  acts  as  a  conductor  of  the 

water   absorbed  from   the  ground  ? 

Make  a  longitudinal  section  through  the  upper  half  of 


124 


ROOTS   AND   UNDERGROUND   STEMS 


your  specimen,  continuing  it  an  inch  or  two  into  the  stem ; 
do  you  find  any  sharp  line  of  division  between  the  two  ? 

175.  The  Active  Part  of  the  Root.—  It  is  only  the  newest 
and  most  delicate  parts  of  the  root  that  produce  hairs  and 

are  engaged  in  the  active 
work  of  absorption,  the 
older  parts  acting  mainly 
as  carriers.  Hence,  old 
roots  lose  much  of  their 
characteristic  structure 
and  take  on  more  and 
more  of  the  office  of  the 
stem,  until  there  is  prac- 
tically no  difference  be- 
tween them.  On  the 
sides  of  gullies,  where 
the  earth  has  been 

262.  —  Root  of  a  tree  on  the  side  of  a  gulley      washed  from  around  the 
acting  as  stem.  r  , 

trees,  we  often  see  the 

upper  portion  of  the  root  covered  with  a  thick  bark  and 
fulfilling  every  office  of  a  true  stem. 

176.  Use  of  the  Epidermis.  —  Cut  away  the  lower  end  of 
a  taproot ;  seal  the  cut  surface  with  wax  so  as  to  make  it 
perfectly  water-tight,  and  insert  it  in  red  ink  for  at  least 
half  the  remaining  length,  taking  care  that  there  is  no 
break  in  the  epidermis.     Cut  an  inch  or  two  from  the  tip 
of  the  lower  piece,  or  if  material  is  abundant,  from  another 
root  of  the  same  kind,  and  insert  it  without  sealing  the  cut 
surface,  in  red  ink,  beside  the  other.     At  the  end  of  three 
or  four  hours,  examine  longitudinal  sections  of  both  pieces. 
Has  the  liquid  been  absorbed  equally  by  both  ?     If  not,  in 
which  has  it  been  absorbed  most  freely  ?     What  conclusion 
would  you  draw  from  this,  as  to  the  passage  of  liquids 
through  the  epidermis  ? 

From  this  experiment  we  see  that  the  epidermis,  besides 
protecting  the  more  delicate  parts  within  from  mechanical 
injury  by  hard  substances  contained  in  the  soil,  serves  bv 


FUNCTION  AND  STRUCTURE  OF  ROOTS     125 

its  comparative  imperviousness  to  prevent  evaporation,  or 
reabsorption  by  the  soil,  of  the  sap  as  it  flows  from  the  root 
hairs  up  to  the  stem  and  leaves. 

177.  The  Branching  of  Roots.  —  Peel  off 
a  portion  of  the  cortex  from  any  branch- 
ing taproot  and  notice  the  hard,  woody 
axis  that  runs  through  the  interior.     Pull 
off  a  branch  from  the  stem  and  one  from 
the  root ;    which  comes  off  most  easily  ? 
Examine  the  points  of  attachment  of  the 
two  and  see  why  this  is  so.     This  mode 
of   branching  from  the  central   axis  in- 
stead of  from  the  external  layers,  as  in 
the   stem,    is   one   of   the   most   marked 
distinctions  between  the  structure  of  the  two  organs. 

178.  Distinctions  between  Root  and  Stem.  —  In  stems 
the  branches  always  occur,  as  we  saw  in  our   study  of 
leaves,  at  regular  intervals  called  nodes  (Sec.  50),  while 
in  the  root  they  occur  quite  irregularly.     The  root  grows 
only  from   just   behind   the   tip;    stems  increase   by   the 
development  of  successive  internodes,  each  of  which  may 
continue  to  grow  for  some  time  after  the  development  of  its 
successor  (Sees.  1 53,  1 57).    The  stem  is  normally  an  ascend- 
ing, the  root  a  descending,  axis ;  the  one  bears  leaves  and 
buds  at  regular  intervals,  the  other  bears  no  leaves  and 
only  occasional  buds  of  the  kind  called  adventitious  ;  that 
is,  buds  which  appear  by  chance,  as  it  were,  at  irregular 
intervals.      There   are   other    distinctions    recognized   by 
botanists,  but  they  are  too  technical  to  be  considered  here. 

PRACTICAL  QUESTIONS 

1 .  Why  will  most  plants  grow  so  much  better  in  an  earthen  pot  or 
a  wooden  box  than  in  a  vessel  of  glass  or  tin?     (168.) 

2.  Which  absorb  most  from  the  soil,  plants  with  light  roots   and 
abundant  foliage  or  those  with  heavy  roots  and  scant  foliage? 

3.  Which  will  require  the  deeper  tillage,  a  bed  of  carrots  or  one  of 
strawberries?     (173.) 


126 


ROOTS   AND    UNDERGROUND    STEMS 


4.  Which  will  best  withstand  drought,  a  crop  of  cotton  or  one  of 
Indian  corn?     Which  will  thrive  best  on  high  and  dry  ground?     (173.) 

5.  Which  will  interfere  least  with  the  nourishment  of  the  trees  if 
planted  in  a  peach  orchard,  cotton  or  oats?     (173.) 

6.  Should  a  crop  of  cotton  and  one  of  hemp  succeed  each  other  on 
the  same  land? 

7.  Why  does  the  gardener  manure  a  grass  plat  by  scattering  the 
fertilizer  on  top  of  the  ground  while  he  digs  around  the  roses  and  lilacs 
and  deposits  it  underground  ? 

8.  Where  should  the  manure  be  placed  to  benefit  a  tree  or  shrub 
with  wide-spreading  roots?     (175.) 

9.  Is  it  a  wise  practice  to  mulch  a  tree  by  raking  up  the  dead  leaves 
and  piling  them  around  the  base  of  the  trunk,  as  is  so  often  done? 
Why,  or  why  not  ? 

10.  Why  are  willows  usually  selected  in  preference  to  other  trees 
for  planting  along  the  borders  of  streams  in  order  to  protect  the  banks 
from  washing? 

FLESHY  ROOTS 

MATERIAL.  —  A  turnip,  or  other  fleshy  root. 
Another  root  of  the  same  kind  that  has  stood  in 
red  ink  for  several  hours. 

179.  Structure  of  Fleshy  Roots.  —  Cut 
away  an  inch  or  two  from  the  tip  of  a 
young  fleshy  root 
of  any  kind,  and 
let  it  stand  from 
six  to  twelve  hours_ 
in  red  ink.  Then 
cut  into  two  or 
three  equal  trans- 
verse sections  and 
observe  the  course 
of  the  fluid. 
Through  what  por- 
tion did  it  rise  most 
readily  ?  Sketch 
one  of  the  sections 
and  compare  it 

264-266. -Shapes  of  fleshy  roots  (GR!Y)  :  264,  napi-    With  y°UI~  drawing 
form;  265,  conical;  266,  spindle-shaped. '  of    the  WOOdy  tap- 


FLESHY   ROOTS  127 

root.  The  ring  of  ink  marks  the  boundary  between  the 
cortex  and  the  central  axis.  Cut  through  one  of  the  sec- 
tions vertically  and  notice  that  the  portion  marked  "  vascu- 
lar cylinder  "  in  the  hard  root  has  here  been  replaced  by 
a  soft,  nutritious  substance.  Put  a  drop  of  iodine  on  it 
and  see  if  it  contains  starch.  Peel  off  a  part  of  the  cortex 
and  observe  that  the  woody  or  conducting  portion  of  the 
interior  is  confined  principally  to  a  thin  layer  on  the  out- 
side of  the  thickened  fleshy  axis.  Can  you  tell  now  why 
the  course  of  the  red  ink  in  this  kind  of  root  is  confined 
mainly  to  a  ring  just  inside  the  cortex,  while  in  hard  roots 
—  in  the  newer,  active  parts  of  them  at  least — it  runs 
through  the  whole  of  the  central  axis?  (Sec.  174.) 

This  band  of  woody  or  vascular  tissue,  as  it  is  called, 
becomes  very  evident  in  old  turnips  and  radishes.  In  the 
beet  it  is  arranged  peculiarly,  being  disposed  in  concentric 
layers  alternating  with  the  fleshy  substance,  instead  of 
in  a  single  layer  next  the  cortex.  These  vascular  rings 
give  to  a  section  of  beet  the  appearance  of  certain  woody 
stems  with  their  rings  of  annual  growth,  but  their  origin 
is  quite  different. 

180.  Function  of  Fleshy  Roots. —What  is  the  use  of 
fleshy  roots  ?     We  give  a  practical  answer  to  this  question 
every  time  we  eat  a  carrot  or  a  turnip.     Fleshy  roots  are 
especially  useful  to  biennials,  a  name  given  to  herbs  that 
take  two  years  to  perfect  their  fruit,  in  contradistinction  to 
annuals,  which  complete  their  life  history  in  a  single  season. 
The  biennials  spend  their  first  year  in  laying  by  a  store  of 
nourishment  which  they  use  up  the  next  year  in  producing 
a  crop  of  seed  —  provided  man  does  not  forestall  them 
and  appropriate  it  to  his  own  use.     This  explains  why  a 
radish  or  a  turnip  is  so  dry  and  tasteless  the  second  year ; 
nearly  all  of  its  store  of  food  has  been  exhausted  in  matur- 
ing seed. 

181.  Perennial  Herbs  are  those  that  live  on  indefinitely 
from  year  to  year.      Many  of   these,  like  the  dahlia  and 
hawkweed,  die  down  above  ground  in  winter  but  are  en- 


128  ROOTS   AND   UNDERGROUND    STEMS 

abled  to  keep  their  underground  parts  alive  through  the 
supply  of  nourishment  stored  in  their  roots,  and  thus  get 
the  advantage  of  their  competitors  by  starting  out  in  spring 
with  a  good  supply  of  food  on  hand.  If  you  will  dig 
around  any  of  our  hardy  winter  herbs,  such  as  the  rib 
grass  (plantain),  dandelion,  and  common  dock,  that  keep 
a  rosette  of  green  leaves  above  ground  all  the  year,  you 
will  generally  find  that  they  have  a  more  or  less  fleshy  tap- 
root full  of  nourishment,  stored  away  underground. 

PRACTICAL  QUESTIONS 

1.  Compare  a  root  of  wild  carrot  with  a  cultivated  one  ;  what  differ- 
ence do  you  see? 

2.  Why  are  the  fleshy  roots  of  wild  plants  so  much  smaller  than 
those  of  similar  species  in  cultivation? 

3.  Why  do  farmers  speak  of  turnips  and  other  root  crops  as  "heavy 
feeders11?     (180.) 

4.  Which  is  most  exhausting  to  the  soil,  a  crop  of  beets,  or  one  of 
oats?     Onions,  or  green  peas? 

5.  Which  is  best  to  succeed  a  crop  of  turnips  on  the  same  land,  hay 
or  carrots? 

6.  Write  out  what  you  think  would  be  a  good  rotation  for  four  or 
five  successive  crops. 

7.  Study  the  following  rotations  and  give  your  opinion  about  them  ; 
suggest  any  improvements  that  may  occur  to  you,  and  give  a  reason  for 
the  change:  Beets,  barley,  clover,  wheat ;  cotton,  oats,  peas,  corn;  oats, 
melons,  turnips ;  cotton,  oats,  corn  and  peas  mixed,  melons ;    cotton, 
hay,  corn,  peas. 

SUB-AERIAL  ROOTS 

MATERIAL.  —  A  hyacinth  bulb  or  a  cutting  of  wandering  Jew  grown 
in  a  glass  of  water.  Specimens  of  any  kind  of  parasitic  plants  that  can 
be  obtained,  such  as  mistletoe,  dodder,  resurrection  fern  {Poly podium 
incanuiii),  etc.  Freshly  rooted  cuttings  of  geranium,  coleus,  or  other 
easily  rooting  twig. 

182.  Subterranean  and  Sub-aerial  Roots.  —  The  roots  we 
have  been  considering  are  all  subterranean  and  bring  the 
plant  into  relation  with  the  earth,  whether  for  purposes  of 
nourishment,  or  of  anchorage  to  a  fixed  support,  or,  as  in 
the  majority  of  cases,  for  both.  But  many  plants  do  not 
get  their  nourishment  directly  from  the  soil,  and  these  give 


SUB-AERIAL   ROOTS  129 

rise  to  the  various  forms  of  sub-aerial  roots,  or  those  that 
grow  above  ground. 

183.  Water    Roots.  —  Large    numbers    of    plants    are 
adapted  to  live  in  the  water,  either  floating  freely,  as  the 
duckweed  (Lemmi)  and  bladderwort  (Utricularia),  or  an- 
chored to  mud  and  sticks  on  the  bottom.     Water  roots  are 
generally  white  and  threadlike  and  more  tender  and  suc- 
culent  than   ordinary  soil  roots.     Many  land   plants  will 
develop  water  roots  and  thrive  on  that  element  if  brought 
into  contact  with  it.     Place  a  cutting  of  wandering  Jew  in 
a  clear  glass  of  water,  and  in  from  four  to  six  days  it  will 
develop  beautiful  water  roots  in  which  both  hairs  and  cap 
are  clearly  visible  to  the  naked  eye. 

The  chief  office  of  ordinary  roots  being  to  absorb  mois- 
ture, they  have  a  great  affinity  for  water,  and  its  presence 
or  absence  exerts  a  strong  determining  influence  on  their 
direction,  often  overcoming  that  of  geotropism  (Sec.  169). 

184.  Parasitic  Plants  are  those  that  live  by  attaching 
themselves  to   some  other   living   organism,   from  which 

they  draw  their  nourishment 
ready  made.  Their  roots  are 
adapted  to  penetrating  the 
substance  of  the  host,  as  their 


267  268 

267,  268.  —  Mistletoe  penetrating  bough  of  oak  :  267,  lower  part  of  stem  attached 
to  branch ;  268,  longitudinal  section  through  one  of  the  haustoria  strands,  showing 
its  progress  as  the  branch  thickens. 

victim  is  called,  and  absorbing  the  sap  from  it.  They  are 
appropriately  named  hanstoria,  a  word  meaning  suckers, 
or  absorbers.  Dodder  and  mistletoe  are  the  best-known 
examples  of  plant  parasites,  though  the  latter  is  only 
partially  parasitic,  as  it  merely  takes  up  the  crude  sap 
from  the  host  and  manufactures  it  into  food  by  means  of 
its  own  green  leaves. 

ANDREWS'S   EOT.  —  9 


1 30  ROOTS   AND  UNDERGROUND    STEMS 

185.  Saprophytes  are  plants  like  the  Indian  pipes  (Mono- 
tropa)  and  squaw  root  (Conopholis)  that  live  upon  dead  and 
decaying  vegetable  matter.  They  are  only  partially  par- 
asitic, and  do  not  bear  the 
haustoria  of  true  parasites. 
A  good  many  plants  that 
appear  to  live  an  honest 
life  above  ground  practice 

269.  — Roots   of   Gerardia  parasitic  under-    a     secret       parasitism      by 

ground^  GRAY).  sending    their    roots   into 

those  of  their  neighbors  beneath  the  soil  and  drawing 
part  of  their  nourishment  from  them.  Among  those  that 
show  a  propensity  to  this  degenerate  habit  are  the  pretty 
yellow  gerardias,  and  their  kindred,  the 
yellow  rattle  (Rhinanthus},  and  the 
Canada  lousewort  (Pedicularis). 

186.  Aerial  Roots  are  such  as  have 
no  connection   at  all  with   the   soil  or 
with   any  host    plant,    except   as    they 
may  lodge  upon  the  trunks  and  branches 
of  trees  for  a  support.     In  our  climate 
aerial  roots  are  generally  subsidiary  to 
soil  roots,  like  the  long  dangling  cords 
that   hang   from   some   species   of    old 

grape  vines  ;  or  they  subserve  other  pur-    ing  on  the  bough  of  a 
poses  altogether  than  absorbing  nourish-    tree  Wter  GRAY)" 
ment,  as  the  climbing  roots  of  the  trumpet  vine  and  poison 
ivy. 

187.  Adventitious  Roots  is  a  name  applied  to  any  kind 
that  occur  on  the  stems  of  plants  or  in  other  unusual  posi- 
tions.    Common  examples  are  the  roots  that  put  out  from 
the  lower  nodes  of  corn  and  sugar  cane  and  serve  both  to 
supply  additional  moisture  and  to  anchor  the  plant  more 
firmly  to  the  soil.     Most  plants  will  develop  adventitious 
roots  if  covered  with  earth  or  even  if  merely  kept  in  con- 
tact with  the  ground.     The  gardener  takes  advantage  of 
this  property  when  he  propagates  by  cuttings  or  layers. 


UNDERGROUND   STEMS  131 

Place  a  cutting  of  rose  geranium  or  of  coleus  in  a  pot  of 
moist  sand.  As  soon  as  the  roots  begin  to  form,  examine 
the  stem  with  a  lens  to  see  from  what  portion  they  spring 


271. —  New  stocks  with  adventitious  roots  produced  by  layering. 

—  whether  from  near  the  circumference,  or  from  the  cen- 
ter. What  part  of  the  stem  should  you  infer  from  this,  is 
most  actively  concerned  in  the  work  of  growth  ? 

PRACTICAL    QUESTIONS 

1 .  Do  the  adventitious  roots  of  such  climbers  as  ivy  and  trumpet 
vine  draw  any  nourishment  from  the  objects  to  which  they  cling? 

2.  How  do  you  know  this? 

3.  Do  they  injure  trees  by  climbing  upon  them ;  and  if  so,  how? 

4.  What  is  the  use  of  the  aerial  roots  of  the  scuppernong  grape  ? 

5.  Is  the  resurrection  fern  (Polypodium  incanuni)  a  parasite  or  an 
air  plant  ? 

6.  On  what  plants  in  your  neighborhood  does  mistletoe  grow  most 
abundantly?     Dodder? 

7.  Is  mistletoe  injurious  to  the  host? 

8.  Name  some  plants  that  are  propagated  mainly,  or  solely,  by  roots 
and  cuttings. 

UNDERGROUND   STEMS 

MATERIAL.  —  Underground  stems  of  couch  grass,  nut  grass,  violet, 
iris,  or  any  rootstocks  obtainable.  In  cities,  if  nothing  better  is  to  be 
had,  some  dried  orris  root  or  calamus  might  be  obtained  from  a  drug- 
gist. Any  kind  of  tuber,  such  as  potato,  artichoke,  Madeira  vine,  etc. 
A  sweet  potato.  A  scaly  lily  bulb  and  one  of  onion  or  hyacinth.  Pota- 
toes and  sweet  potatoes  treated  with  red  ink. 

188.  Rootstocks.  —  So  like  fleshy  roots  are  certain  thick- 
ened underground  stems  that  it  is  not  always  easy  to  dis- 
tinguish between  them.  So  long  as  the  stem  remains  above 


132 


ROOTS   AND    UNDERGROUND    STEMS 


ground  there  is  little  danger  of  mistaking  its  identity,  even 
when  it  puts  forth  roots  from  every  node,  like  the  creeping 
stems  of  Bermuda  grass  and  couch 
grass.  Even  in  such  underground 
stems  as  those  of  the  mint  and  couch 
grass  their  real  nature  is  evident  from 


273.  —  Rootstock  of  creep- 
ing panic  grass. 


272.  —  Running  rootstock  of  peppermint  (GRAY). 

the  regular  nodes  into  which  they  are 

divided,    and   the    scales  which   they 

bear  instead  of  leaves.     Stems  of  this 

kind    are    called    rootstocks.      They 

usually   send    out    roots    from    every 

node  and  are  the  most  ineradicable  pests  the  farmer  has 

to  contend  with,  since  each  joint  is  capable  of  developing 

into  a  new  plant,  and  chopping  them  to  pieces  serves  only 

to  aid  in  their  propagation. 

189.  Rhizomas.  —  Rootstocks  do  not  always  retain  their 
stemlike  nature  so  plainly,  but  are  commonly  more  or  less 
shortened  and  thickened,  as  in  the  violet,  iris,  bulrush, 
sweet  flag,  bloodroot,  etc.,  and  it  is  to  this  condition  that  the 
name  rhizoma  is  usually  applied.  A  typical  example  of 
the  rhizoma  is  that  of  the  Solo- 
mon's seal  (Fig.  274.)  The  pecul- 
iar scars  from  which  it  takes  its 
name  are  caused  by  the  falling 

274- -Rhizoma    of    Solomon's     awav  each    year    of    tne    flowering 
seal  (after  GRAY). 

stem  of  the  season,  after  its  work 

is  done,  leaving  behind  the  joint  or  node  of  the  under- 
ground stem  from'  which  it  originated.  Thus  the  plant 
lives  on  indefinitely,  growing  and  increasing  at  one  end 
as  fast  as  it  dies  at  the  other.  The  joints  on  the  rhizoma 
mark,  not  the  age  of  the  plant,  but  of  each  joint  or 
internode.  If  there  are  two  or  three  joints,  this  indicates 


UNDERGROUND    STEMS  133 

that  the  oldest  of  them  is  two  or  three  years  old,  as  the 
case  may  be. 

Examine  a  rhizoma  of  the  iris,  or  any  other  specimen 
obtainable.  How  many  joints  do  you  find?  Where  is  the 
oldest  ?  How  old  is  it  ?  Are  they  all  entirely  under- 
ground ?  Where  do  the  true  roots  spring  from  ?  The 
flower  stems  ?  Notice  the  rings  or  ridges  that  run  across 
the  upper  side  of  each  joint.  These  are  the  leaf  scars, 
and  each  scar  marks  one  of  the  very  short  internodes  of 
the  past  season's  growth.  At  the  nodes,  in  the  axils  of 
the  leaf  scars,  buds  frequently  occur,  producing  other 
joints,  which  may  be  considered  branches,  and  it  is  these 
branches  that  give  to  the  rootstocks  of  the  iris  and  black- 
berry lily  their  thick,  matted  appearance.  How  many 
leaves  did  last  year's  joint  of  your  specimen  bear,  and 
how  many  internodes  had  it  ? 

190.  Tubers.  —  When  a  rhizoma  is  very  greatly  enlarged, 
as  in  the  artichoke  and  potato,  it  is  called  a  tuber.  Its 
real  nature  in  such  cases  is  often  very  much  disguised, 
but  a  little  study  will  make  it  clear.  The  so-called  root  of 
wild  smilax  shows  very  plainly 
the  gradations  from  leaves  to 
scales  and  from  stem  to  tuber. 

In  the  typical  tuber,  of  which 
the  potato  is  the  most  familiar 
example,  the  internodes  are  so 
thickened  and  shortened  as  to 
have  lost  all  resemblance  to  a 
stem,  but  their  nature  is  revealed 
by  the  eyes.  These  are  really 
nothing  else  than  buds  growing  275,  276.  -  Tubers  (after 
in  the  axils  of  leaves,  which  are  GRAY):  275,  forming  potatoes; 

276,  young  potato  enlarged. 

represented  in  the  potato  by  the 

little  scale  that  forms  the  lid  to  the  eye.  (In  an  old  potato 
the  scales  will  probably  have  disappeared ;  try  to  get 
fresh  ones  for  examination,  and  if  possible,  with  some  of 
the  attaching  stems  still  remaining.  The  artichoke  and 


134  ROOTS  AND   UNDERGROUND   STEMS 

tubers  of  the  Madeira  vine  also  make  good  objects  for 
study.)  Notice  the  arrangement  of  the  eyes,  or  buds;  is 
it  alternate  or  opposite?  How  many  ranked?  Make  a 
sketch  of  the  potato  as  it  appears  on  the  outside.  Make 
a  similar  sketch  of  the  sweet  potato,  and  compare  the 
two.  Is  there  any  scale  below  the  eye  in  the  sweet 
potato  ?  Do  the  eyes  occur  in  any  regular  order  ? 

191.  Make  a  cross  section  of  each,  and   sketch  them. 
Notice  the  thin  dark  ring  that  runs  around  the  inside  of  the 
potato  at  some  distance  from  the  circumference.     Label 
this  -vascular  tissue;  the  loose  porous  layer  between  it  and 
the  skin,  cortex ;  the  central  portion  within  the  vascular  ring, 
pith;  and  the  outer  skin,  epidermis.     See  if  you  can  find 
corresponding  parts  in  the  sweet  potato,  and  label  them. 

Put  one  of  the  cut  ends  of  each  in  red  ink  (this  should 
have  been  attended  to  before  the  recitation),  let  them  stand 
four  to  five  hours,  then  make  sections  parallel  to  the  cut 
surface  till  you  reach  the  point  where  the  red  ink  has  pene- 
trated ;  what  difference  do  you  notice  ?  Which  has  the 
thicker  cortex  ?  Compare  the  behavior  of  the  potato  with 
that  of  the  turnip  treated  with  red  ink  in  Section  179. 
What  would  you  infer  from  this  as  to  the  office  of  the  woody 
tissue  ?  What  is  the  office  of  the  epidermis  ?  If  you  are 
in  doubt,  peel  a  tuber  and  weigh  it.  At  the  same  time 
weigh  one  of  about  the  same  size  from  which  the  skin  has 
not  been  removed,  and  put  the  two  side  by  side  in  a  dry 
place.  At  the  end  of  three  or  four  days  weigh  them  again 
and  see  which  has  lost  the  most. 

We  have  learned  that  roots  are  not  divided  into  nodes, 
that  they  never  bear  leaves,  that  they  branch  quite  irreg- 
ularly, and  that  they  sometimes  bear  adventitious  buds. 
Now  can  you  state  some  of  the  reasons  why  the  potato 
is  regarded  as  a  stem  and  the  sweet  potato  as  a  root  ? 

192.  Storage  of  Nourishment.  —  The  object  of   both   is 
the  same,  the  storage  of  nourishment.     Drop  a  little  iodine 
on    each    and    see    what    this    nourishment    consists    of. 
Which  contains  the  more  starch? 


UNDERGROUND   STEMS 


135 


It  is  this  abundant  store  of  food  that  makes  the  potato 
such  a  valuable  crop  in  cold  countries  like  Norway  and 
Iceland,  where  the  seasons  are  too  short  to  admit  of  the 
slow  process  of  developing  the  plant  from  the  seed. 

193.  The  Bulb  is  a  form  of  underground  stem  reduced 
to  a  single  bud.  Get  the  scaly  bulb  of  a  white  garden  lily, 
and  sketch  it  from  the  outside  and  in  cross  and  vertical 
section.  Compare  it  with  the  scaly  winter  buds  of  the  oak 
and  hickory  or  other  common  deciduous  tree.  Make  an 
enlarged  sketch  of  the  latter  on  the  same  scale  as  the  lily, 
and  the  resemblance  will  at  once  become  clear.  The 
scales  of  the  bulb  are,  in  fact,  only  thick,  fleshy  leaves 


277.  —  Scaly          278.  —  Scaly  bulb  of 
bud     of     oak  lily  (GRAY), 

enlarged. 


279.  —  Bulblets  in  the  axils 
of  the  leaves  of  a  tiger  lily 
(GRAY). 


closely  packed  round  a  short  axis  that  has  become  dilated 
into  a  flat  disk.  From  the  terminal  node  of  this  trans- 
formed stem,  i.e.,  the  center  of  the  disk,  rises  the  flower 
stalk,  or  scape,  as  it  is  called,  of  the  season.  After  blos- 
soming, the  scape  perishes  with  its  bulb,  and  their  place  is 
taken  by  new  ones  which  are  developed  from  the  axils  of 
the  scales,  thus  revealing  their  leaflike  nature. 

That  bulbs  are  only  modified  buds  is  further  shown  by 
the  bulblets  that  sometimes  appear  among  the  flowers  of 
the  onion,  and  in  the  leaf  axils  of  certain  lilies.  They 
never  develop  into  branches,  but  drop  off  and  grow  into 
new  plants  just  as  the  subterranean  bulbs  do. 

194.  Tunicated  Bulbs.  —  Compare  an  onion  or  a  hya- 
cinth bulb  with  a  lily  bulb.  In  what  respect  does  it  differ 
from  the  lily  bulb  ?  Pull  off  the  outer  layers,  which  have 


136 


ROOTS  AND  UNDERGROUND   STEMS 


onion  ;      281,    vertical 
section  of  a  tulip  bulb, 


become  dry  and  papery,  and  observe  how  the  inner  fleshy 
ones  encircle  one  another  successively. 
A  bulb  of  this  kind,  made  up  of  succes- 
sive layers,  is  said  to  be  tunicated.  Look 
for  the  flower  cluster  in  the  center.  Do 
you  find  any  axillary  bulbs  ?  Any  axil- 
lary scapes?  Compare  the  concentric 
rings  of  a  tunicated  bulb  as  seen  in 
cross  section  with  those  of  the  beet; 
are  they  of  the  same  nature  ?  Before 
answering,  look  again  at  your  cross  sec- 
tion of  the  lily  bulb  and  think  what 
would  happen  if  the  scales  were  to  be 
broadened  sufficiently  at  the  base  for 
each  one  to  encircle  completely  all  within 

bulbs'  ^GRAY)1?10^,    it.     Compare  the  leaves  and  scales  of 

cross     section    of    an     tjle    Omon    With    the    leaf- 

stalk    of    the     sycamore 
(Fig.  20),  and  see  if  you 
can  find   any  reason   for 
regarding  them  as  modified  petioles. 

195 .  Uses  of  Underground  Stems. — Though 
the  chief  function  of  underground  stems  is 
the  storage  of  nourishment,  they  serve  other 
purposes  also.  In  plants  like  the  ferns,  that 
require  a  great  deal  of  moisture,  and  in 
others  growing  in  dry  places,  like  the  blackberry  lily,  that 
need  to  husband  it  carefully,  they  may  be  useful  in  pre- 
venting the  too  rapid  evaporation  that  would  take  place 
through  aerial  stems.  Defense  against  frost,  cold,  heat, 
and  other  dangers,  as  well  as  quickness  of  propagation, 
are  also  attained,  or  assisted  by  this  means. 

PRACTICAL  QUESTIONS 

1.  Name  some  plants  in  your  neighborhood  that  are  propagated  by 
rootstocks  ;  by  rhizomas ;  by  tubers. 

2.  What  is  the  advantage  of  propagating  in  this  way  over  planting 
the  seed?    (192,  195.) 


282.  —  Leaf  of 
an  onion  divided 
lengthwise. 


PLANT   FOOD  137 

3.  What  other  advantages,  if  any,  does  each  of  the  plants  named 
gain  from  its  earth-seeking  (geophilous)  habit? 

4.  What  makes  the  nut  grass  so  troublesome  to  farmers  ? 

5.  Is  its  nut  a  root,  or  a  tuber?     How  can  you  tell?    (190,  191). 

6.  Suggest  some  ways  for  destroying  weeds  that  are  propagated  in 
this  way. 

7.  Could  you  get  rid  of  wild  onions  in  a  pasture  by  mowing  them 
down?     By  digging  them  up?    (193.) 

8.  Is  it  wise  for  farmers  to  neglect  the  appearance  of  such  a  weed 
in  their  neighborhood,  even  though  it  does  not  infest  their  own  land  ? 

9.  Name  any  plants  of  your  neighborhood,  either  wild  or  cultivated, 
that  are  valued  for  their  rhizomas  ;  for  their  tubers. 

10.  What  part  of  the  plants  named  below  do  we  use  for  food  or 
other  purposes?     Ginger,  angelica,  ginseng,  cassava,  arrowroot,  garlic, 
onion,  sweet  flag,  iris,  sweet  potato,  Cuba  yam,  artichoke. 

1 1 .  Why  are  the  true  roots  of  bulbous  and  rhizome  bearing  plants 
generally  so  much  smaller  in  proportion  to  the  other  parts  than  those  of 
ordinary  plants?     (192.195.) 

12.  If  the  Canada  thistle  grows  in  your  vicinity,  examine  the  roots 
and  see  if  there  is  anything  about  them  that  will  help  to  account  for  its 
hardihood  and  persistency. 

13.  If  you  live  in  the  region  of  the  horse  nettle  (Solanum  caroli- 
nense),  explain  how  it  is  enabled  to  flourish  in  such  hard  and  forbidding 
places. 

PLANT  FOOD 

MATERIAL.  —  An  ounce  or  two  each  of  different  kinds  of  seeds,  and  a 
lamp  stove  or  other  convenient  means  of  drying  them.  A  pair  of  scales. 

196.  Solids,  Liquids,  and  Gases.  —  The  habit  of  storing 
up  food  in  some  part  of  their  structure  for  future  use  is 
practically  universal  among  plants.  Let  us  now  inquire 
what  this  food  consists  of  and  where  it  comes  from. 

Take  a  quantity  of  seeds  of  different  kinds  (about  thirty 
grams  of  each,  or  one  ounce  approximately,  will  answer), 
weigh  each  kind  separately  and  then  dry  them  at  a  high 
temperature,  but  not  high  enough  to  scorch  or  burn  them. 
After  they  have  become  perfectly  dry,  weigh  them  again. 
What  proportion  of  the  different  seeds  was  water,  as  indi- 
cated by  their  loss  of  weight  in  drying? 

Burn  all  the  solid  part  that  remains,  and  then  weigh  the 
ash.  What  proportion  of  each  kind  of  seed  was  of  incom- 


13* 


ROOTS   AND    UNDERGROUND    STEMS 


bustible  material  ?     What  proportion  of  the  solid  material 
was  destroyed  by  combustion  ? 

Test  in  the  same  way  the  fresh,  active  parts  of  any  kind 
of  ordinary  land  plant  (sunflower,  hollyhock,  pea  vines,  etc., 
make  good  specimens)  and  of  some  kind  of  succulent  water 
or  marsh  plant  (Sagittaria,  water  lily,  fern,  etc.).  Do  you 
notice  any  difference  in  the  amount  of  water  given  off  and 
of  solid  matter  left  behind  ?  In  the  character  of  the  ashes 
left?  Have  you  observed  in  general  any  difference  be- 
tween the  ashes  of  different  woods ;  as,  for  instance,  hick- 
ory, pine,  oak,  etc.  ? 

197.  Essential  Constituents.  —  The  composition  of  the 
ash  of  any  particular  plant  will  depend  upon  two  things : 
the  absorbent  capacity  of  the  plant  itself  and  the  nature 
of  the  substances  contained  in  the  soil  in  which  it  grows. 
But  chemical  analysis  has  shown  that  however  the  ashes 
may  vary,  they  always  contain  some  proportion  of  the  fol- 
lowing substances  :  potassium  (potash),  calcium  (lime),  mag- 
nesium, phosphorus,  a"nd  (in  green 
plants)  iron.  These  elements  occur 
in  all  plants,  and  if  any  one  of  them 
is  absent,  growth  becomes  abnormal 
if  not  impossible. 

The  part  of  the  dried  substances 
that  was  burned  away  after  expelling 
the  water  consists,  in  all  plants, 
mainly  of  carbon,  hydrogen,  oxygen, 
nitrogen,  and  sulphur,  in  varying 
proportions.  These  five  rank  first 
in  importance  among  the  essential 
elements  of  vegetable  life,  and  with- 
out them  the  plant  cell  itself,  the 
physiological  unit  of  vegetable  struc- 
ture, could  not  exist  They  compose 
the  greater  part  of  the  substance  of 
every  plant,  carbon  alone  usually 
forming  about  one  half  the  dry 


283.  —  Water  cultures  of 
buckwheat,  showing  effect 
of  the  lack  of  the  different 
food  elements :  I,  with  all 
the  elements  ;  2,  without 
potassium  ;  3,  with  soda 
instead  of  potash;  4,  with- 
out calcium ;  5,  without  ni- 
trates or  ammonia  salts. 


PLANT   FOOD 


139 


weight.  Other  substances  may  be  present  in  varying 
proportions,  but  the  two  groups  named  above  are  found 
in  all  plants  without  exception,  and  so  we  may  conclude 
that  (with  the  possible  addition  of  chlorine)  they  form  the 
indispensable  elements  of  plant  food.  Carbon,  hydrogen, 
oxygen,  nitrogen,  sulphur,  and  phosphorus  compose  the 
structure  of  which  the  plant  is  built.  The  other  four  do 
not  enter  into  the  substance  as  component  parts,  but  aid 
in  the  chemical  processes  by  which  the  life  functions  of 
the  plant  are  carried  on,  and  are  none  the  less  essential 
elements  of  its  food.  Figure  283  shows  the  difference 
between  a  plant  grown  in  a  solution  where  all  the  food 
elements  are  present  and  others  in  which  some  of  them 
are  lacking. 

198.  How  Plants  obtain  their  Food.  —  With  a  few  doubt- 
ful exceptions,  plants  cannot  assimilate  their  food  unless 
it  is  in  a  liquid  or  gaseous  form.  Of  the  gases,  carbon 
dioxide,  oxygen,  and  hydrogen  can  be  freely  absorbed  from 
the  air  or  from  water 
with  various  substances 
in  solution,  but  most 
plants  are  so  constituted 
that  they  cannot  absorb 
free  nitrogen  from  the 
air  ;  they  can  take  it  only 
in  the  form  of  compounds 
from  nitrates  dissolved 
in  the  soil,  and  hence  the 

importance  of  ammonia  284.— Roots  of  soy  bean  bearing  tubercle- 
and  Other  nitrogenous  forming  bacteria. 

compounds  in  artificial  fertilizers.  Some  of  the  pea  family, 
however,  bear  on  their  roots  little  tubers  formed  by  minute 
organisms  called  bacteria,  which  have  the  power  of  ex- 
tracting nitrogen  directly  from  the  free  air  mingled  with 
the  soil ;  and  hence,  wherever  these  tuber-bearing  legumes 
are  present  the  soil  is  found  to  be  enriched  with  nitrogen 
in  a  form  ready  for  use. 


1 40  ROOTS   AND   UNDERGROUND   STEMS 

Plants  also  obtain  their  supply  of  the  various  mineral 
salts  needed  by  them  from  solutions  in  the  soil  water  which 
they  absorb  through  their  roots.  Different  species,  and 
even  different  varieties  of  the  same  species,  absorb  these 
substances  in  very  different  proportions,  and  upon  this 
fact,  much  more  than  upon  the  form  of  roots  (Sec.  173), 
depends  the  principle  of  the  rotation  of  crops  in  farming. 

199.  Plants  can  not  choose  their  Food.  —  Substances  are 
often  found  in  plants  which  appear  to  be  useless,  and  some, 
as  zinc  and  lead,  which  are  positively  harmful.    This  shows 
that  the  roots  are  not  able  to  choose  their  own  nourishment, 
but  absorb  whatever  is  present  in  the  soil  in  soluble  form 
and  can  penetrate  their  cell  walls.     It  is  not  safe,  there- 
fore, to  conclude  merely  because  a  substance  is  found  in  a 
plant  that  it  should  constitute  a  part  of  its  food.     Neither 
can  we  always  be  sure  that  because  a  plant  will  grow  in 
a  certain  soil  this  is  the  best  soil  for  it,  since  its  presence 
there  may  be  due  merely  to  adaptation  or  toleration,  and 
it  might  do  better  if  given  a  chance  somewhere  else.     All 
these  circumstances  present  matter  for  careful  discrimina- 
tion by  the  farmer. 

200.  Food  Manufacture.  —  The  proportion  of  ash  found 
in  green  plants  increases  from  the  roots  upwards  to  the 
leaves,   thus  showing  that  the  latter  are   the    organs   in 
which   the   manufacturing   or   building-up   process    takes 
place,  and  its  products  are  most   abundant  there.     The 
first  article  of  food  to  be  recognized  is  starch,  but  others 
also  occur  and  are  distributed  to  the  parts  where  they  are 
needed.     Of  course  solid  substances  like  starch  and  the 
various  ashes  that  we  find  in  the  structure  of  plants  can 
not  pass  through  the  walls  of  the  cells  unchanged,  but 
must  be  reduced  to  the  form  of  a  solution.     In  the  case  of 
substances  that  are  insoluble  they  must  first  be  transformed 
to  soluble  ones  and  then  reformed  into  their  original  con- 
stitution, so  we  see  that  the  nutrition  of  plants  is  a  very 
complicated  process,  involving  repeated  chemical  changes 
and  redistributions  of  material. 


PLANT   FOOD  141 

PRACTICAL  QUESTIONS 

1.  Will   a  pound  of  pop  corn  weigh   the  same  after  it   has  been 
"popped"?     (196.) 

2.  Could  any  plant  grow  in  a  soil  from  which  nitrogen  was  entirely 
lacking?     Phosphorus?     Potash?     Lime?     (197.) 

3.  Could   it  live  in  an  atmosphere  devoid  of  oxygen?     Nitrogen? 
Carbon  dioxide?     (197.) 

4.  Is  the  same  kind  of  fertilizer  equally  good  for  all  kinds  of  soil? 
For  all  kinds  of  plants?     (198.) 

5.  Is  starch  soluble  in  water? 

6.  How  does  it  get  from  the  leaves  where  it  is  manufactured  to  the 
rootstocks  where  it  is  stored?     (200.) 

7.  Why  does  too  much  watering  interfere  with  the  nourishment  of 
plants? 

8.  Are  ashes  fit  for  fertilizers  after  being  leached  for  lye?    (197,  198.) 

9.  Why  will  any  but  very  small  shrubs  be  dwarfed,  or  make  very 
slow  growth  in  pots?     (197,  198.) 

FIELD  WORK 

Examine  the  underground  parts  of  hardy  winter  herbs  in  your  neigh- 
borhood, and  of  any  weeds  or  grasses  that  are  particularly  trouble- 
some, and  see  if  there  is  anything  about  the  structure  of  these  parts  to 
account  for  their  persistence.  Note  the  difference  in  the  roots  of  the 
same  species  in  low,  moist  places  and  in  dry  ones  ;  between  those  of  the 
same  kind  of  plants  in  different  soils ;  in  sheltered  and  in  exposed  situ- 
ations. Study  the  direction  and  position  of  the  roots  of  trees  and 
shrubs  with  reference  to  any  stream  or  body  of  water  in  the  neighbor- 
hood. (The  elm,  fig,  mulberry,  and  willow  are  good  subjects  for  such 
observations.)  Notice  also  whether  there  is  any  relation  between  the 
underground  parts  and  the  leaf  systems  of  plants  in  reference  to  drain- 
age and  transpiration. 

Observe  the  effect  of  root  pull  upon  low  herbs.  Look  along  washes 
and  gullies  for  roots  doing  the  office  of  stems,  and  note  any  changes  o't 
structure  consequent  thereon.  Study  the  relative  length  and  strength 
of  the  root  systems  of  different  plants,  with  reference  to  their  value  as 
soil  binders,  or  their  hurtfulness  in  damaging  the  walls  of  cellars,  wells, 
sewers,  etc.  Dig  your  trowel  a  few  inches  into  the  soil  of  any  grove  or 
copse  you  happen  to  visit,  and  note  the  inextricable  tangle  of  roots,  and 
consider  the  fierce  competition  for  living  room  in  the  vegetable  world 
that  it  implies. 

Tests  might  be  made  of  the  different  soils  in  the  neighborhood  of 
the  schoolhouse  by  planting  seeds  of  different  kinds  and  noting  the 
rate  of  germination  ;  first,  without  fertilizers,  then  by  adding  the  differ- 
ent elements  in  succession  to  see  which  is  lacking.  The  field  for  study 
suggested  by  this  subject  is  almost  inexhaustible. 


VI.     THE   STEM    PROPER 

STEM  FORMS  AND  USES 

MATERIAL.  —  Stems  of  various  kinds  —  woody,  herbaceous,  round, 
square,  triangular,  jointed,  upright,  etc.  Herbaceous  stems  are  not 
abundant  in  winter,  but  a  few  hardy  herbs  like  shepherd's  purse,  dande- 
lion, winter  cress  (Barbarea),  dead  nettle,  or  some  of  the  garden 
biennials  can  generally  be  found.  Of  triangular  and  jointed  stems  any 
of  the  sedges  and  grasses  will  furnish  examples.  Have  young  speci- 
mens of  some  kind  of  twining  stems  raised  in  the  schoolroom.  Hop 
and  morning-glory  make  very  good  examples. 

201.  Woody  and  Herbaceous  Stems. — Aerial   stems,   or 
those  above  ground,  are  commonly  ranked  in  two  general 
classes,  woody  and  herbaceous.     The  latter  are  more  or  less 
succulent,  and  die  down  after  fruiting ;  the  former  live  on 
from  year  to  year,  sometimes,  as  in  the  case  of  the  giant 
sequoias  of  California  and  some  of  the  primitive  cypresses 
of  our  own  southern  swamps,  even  for  thousands  of  years. 
Many    herbaceous    stems,    like    the    garden     geraniums 
and   the   common    St.   John's-wort,  show   a   tendency  to 
become  woody,  especially  toward   the  base,  and  live  on 
from   year  to  year.     Woody-stemmed   annuals,  like   the 
cotton  and   castor-oil   plant   are   not,  properly  speaking, 
herbs.      In  the  tropical  countries  to  which  they  belong, 
they  are  perennial   shrubs,  or   even   small  trees,  but   on 
being  transplanted  to  colder  regions,  have  taken   on  the 
annual  habit  as  an  adaptation  to  climate. 

202.  Direction  and  Habit  of  Growth.  — As  to  manner  of 
growth,  there  are  all  forms,  from  the  upright  boles  of  the 
beech  and  pine  to  the  trailing,  prostrate,  and  creeping  stems 
of  which  we  have  examples  in  the  running  periwinkle,  the 
prostrate  spurge,  and  the  creeping  partridge  berry  (Mitch- 

142 


STEM   FORMS  AND   USES 


143 


285.  —  Prostrate   stem   of  Lycopodium   with 

bran4es. 


ella\  respectively.     Prostrate  and  trailing  stems  are  very 

apt  to  become  creepers  by  the  development  of  adventitious 

roots  at  their  nodes, 

wherever   they  come 

in    contact   with    the 

soil.      Between     the 

extremes  of  prostrate 

and    upright,     stems 

may    be    in    various 

degrees, 

Assurgent,  that  is, 
ascending,  like  com- 
mon crab  grass  and 
spotted  spurge  (Eu- 
phorbia maculata\  or, 

Declined  m&  droop- 
ing, as  the  garden  jessamine,  the  matrimony  vine  (Lycium\ 
and  some  of  the  garden  spireas.     The  most  interesting  of 
all  in  their  mode  of  growth  are  the  various  forms  of 

203.  Twining  and  Climbing  Stems. — The  former  rise  from 
the  ground  by  twisting  themselves  spirally  round  their  sup- 
port, like  the  morning-glory,  hop, 
and  yellow  jessamine ;  the  latter 
by  attaching  themselves  to  other 
objects  by  means  of  adventitious 
roots  and  tendrils,  as  the  Virginia 
creeper,  poison  ivy,  pea,  grape, 
smilax,  etc.  A  curious  fact  about 
twiners  is  that  with  one  or  two 
exceptions  each  species  usually 
coils  uniformly  in  the  same  direc- 
tion and  can  not  be  made  to 
change.  Raise  a  young  hop  or 
morning-glory  plant  in  the  school- 

the'su0nnVOlVUlUS  tWini"S  aga'nSt    room'  notice  whether  it  starts  to 

coil  from  right  to  left  or  from  left 

to  right,  and  see  if  you  can  coax  it  to  grow  in  the  opposite 


287 

287.  —  Twining    stems  : 
hop  twining  with   the  sun; 


I44  THE   STEM   PROPER 

direction.  When  it  has  reached  the  end  of  its  stake  suffer 
it  to  grow  about  five  centimeters  (two  inches,  approxi- 
mately) beyond,  and  watch  the  revolution  of  the  tip.  Cut 
a  hole  through  the  center  of  a  piece  of  cardboard  about 
fourteen  centimeters  (five  to  six  inches)  in  diameter,  slip  it 
over  the  loose  end  of  the  stem,  and  fasten  it  to  the  stake 
in  a  horizontal  position  with  a  pin.  Note  the  position  of 
the  stem  tip  every  two  hours  and  mark  on  the  cardboard ; 
how  long  does  it  take  to  complete  a  revolution  ? 

204.  The  Cause  of  Twining  is  believed  to  be  unequal 
growth  on  the  two  sides  of  the  stem  (Sec.   162)  which 
causes   the  tip   to   revolve   slowly  in  a  spiral  toward  the 
side  where  growth  is  slowest.     Run  a  gathering  thread  in 
one  side  of  a  narrow  strip  of  muslin,  about  a  meter  (one 
yard,  approximately)  long,  and  notice  how  the  ruffle  thus 
drawn  will  curl  into  a  spiral  when  allowed  to  dangle  from 
the  needle.     In  the  same  way  the  tension  resulting  from 
unequal  growth  causes  the  stems  and  tendrils  of  climbing 
plants  to  form  themselves  into  spirals. 

Hardly  any  kind  of  stem  grows  at  a  uniform  rate  in  all 
its  parts.  Ordinarily  the  inner  part  grows  most  rapidly. 
Split  the  stem  of  a  fresh  dandelion,  hyacinth,  or  other  herba- 
ceous scape  longitudinally,  and  immerse  it  in  fresh  water 
for  30  to  45  minutes.  Notice  how  the  two  halves  curve 
outward,  or  even  coil  up  like  a  watch  spring*.  This  is  on 
account  of  the  tension  caused  by  the  more  rapid  absorption 
of  the  internal  tissues,  which,  when  relieved  of  the  resist- 
ance of  the  outer  wall,  or  epidermis,  stretch  themselves, 
as  it  were,  but  are  held  back  and  drawn  into  a  curve  by 
the  resistance  of  the  slower  growing  outer  parts,  as  the 
muslin  of  our  ruffle  was  curled  by  the  gathering  thread. 

205.  The  Object  of  the  Various  Forms  of  Stem  Growth 
is  in  all  cases  the  same ;  to  bring  the  leaves  into  the  best 
possible  relations  with  the  light  and  air.     The  stem,  besides 
other  important  uses,  serves  as  a  mechanical  support,  or 
framework,  to  bind  the  other  organs  together,  and  they  are 
largely  dependent  upon  it  for  proper  exposure  to  light 


STEM    FORMS   AND   USES  145 

and  air.  In  general,  leaves  seek  the  best  possible  light 
exposure,  and  hence  the  normal  growth  of  the  stem  is 
upward,  toward  the  light.  There  are  exceptions,  how- 
ever, in  the  case  of  shade-loving  plants  that  seek  the 
shelter  of  the  forests,  and  certain  winter  green  herbs  like 
the  chickweeds,  Indian  strawberry,  and  dandelion,  that 
protect  themselves  against  stress  of  weather  by  lying  low 
and  hugging  the  earth.  The  same  habit  may  temper  both 
the  summer's  heat  and  winter's  cold,  by  shading  the  earth 
around  the  roots  and  preventing  too  rapid  evaporation  in 
the  hot  season,  and  by  keeping  them  in  contact  with  the 
warm  earth  and  preventing  too  rapid  radiation  in  winter. 

206.  The  Surface  of  Stems,  like  that  of  leaves,  may  be 
hairy,  prickly,  smooth,  rough,  etc.,  and  the  same  terms  are 
used  in  describing  them.     The  object  of  these  adaptations 
is  the  same  as  in  leaves.     Grooves  and  wings  and  hairs 
may  either  be  related  to  drainage  and  aid  in  the  conduc- 
tion of   water,  or  they  may  help  or  hinder  the  visits  of 
certain  insects  and  other  animals.     Some  of  these  devices 
are  very  ingenious,  and  have  been  imitated  by  man.     The 
sticky  gum  exuded  from  the  upper  nodes  of  the  catchfly 
(Silcne)  protects  the  flower  against  the  visits  of  crawling 
insects  as  effectively  as  would  a  strip  of  sticky  fly  paper ; 
and  our  barbed-wire  fences  do  not  serve  their  purpose  any 
better  than   the   prickles   of   the  black- 
berry and  the  cactus.     In  regard  to 

207.  Shape,    stems    are    either   round 
(terete),  flattened,  square,  triangular,  etc. 
Sometimes  the  shape  is  of  great  use  in 
helping  to  distinguish  different  kinds  of 
plants.     In  the  mint  family  and  its  allies, 
square  stems  are  prevalent ;  the  sedges 
are  generally  characterized  by  triangular 
ones,    and    grasses    by    round,    hollow, 
jointed    culms,    or   haulms,    as    they  are 
called,    like   those   of   wheat,    oats,    and 

ry6-  288.  —  Culm  of  millet. 

ANDREWS'S   EOT.  —  IO 


146 


THE   STEM   PROPER 


208.  Runners  and  Stolons,  of  which  we  have  familiar 
examples  in  the  strawberry  and  currant  respectively,  are 
stems  or  branches  by  which  plants 
propagate  themselves  above  ground 
as  readily  as  by  rootstocks  under- 
ground. Suckers  are  shoots  from 
adventitious  root  buds.  The  rose, 
raspberry,  blackberry,  and  asparagus 
are  propagated  almost  entirely  by 
their  means.  The  little  shoots,  called 
by  gardeners  scions,  that  spring  up 
around  the  foot  of  apple  and  pear 
trees,  and  many  others,  have  a  simi- 
lar origin. 

289.  —  Orange  hawkweed 

209.   Modifications  of  the  Stem.  - 

Like  leaves,  the  stem  is  subject  to  many  modifications, 
and  is  made  to  serve  various  purposes 
other  than  its  normal  ones.  With  some 
of  these  we  have  already  become 
acquainted  in  its  underground  condition. 
Aerial  stems  frequently  serve  like  pur- 
poses. The  sugar  cane  carries  a  rich 
supply  of  sweets  in  its  juicy  internodes, 
and  cabbage  stalks  also  are  well  stocked 
with  food  before  flowering.  In  the 
cactus  family,  which  inhabit  dry  and 
desert  regions,  where  the  scanty  mois- 
ture they  draw  from  the  earth  would  be 
too  rapidly  exhaled  from  the  expanded 
surface  of  leaves,  the  foliage  has  either 
disappeared  altogether  or  been  reduced 
to  mere  spines,  while  the  greatly  thick- 
ened stems  have  taken  upon  themselves 

the  triple  Office   of  leaf,  Stalk,  and  Store-     storage   and    preserva- 

room.     Examine  a  potted  cactus,  or  a    " 

joint   of   the  common  prickly  pear,  and  notice  how  the 

tvhole  plant  has  been  compacted  into  a  form  that  exposes 


STEM   FORMS   AND   USES  147 

the  least  possible  extent  of  surface  in   proportion  to  the 
substance  contained  in  it. 


210.  Weapons  of  Defense.  —  Examples  of  these  may  be 
seen  in  the  thorns  of  the 
honey  locust,  the  hawthorn, 
and  old  field  plums.  An 
examination  of  the  haw, 
crab  tree,  plum,  and  pear 
will  show  stems  in  all  stages 
of  transformation  from 
short,  stubby  branches  to 
well-defined  thorns.  This 
kind  of  thorn  must  not  be 
confounded  with  briers  or 
prickles  like  those  of  the 
rose  and  smilax,  which  are 

mere  appendages  of  the  epi-          291.  — Thorn  branches  of  Holocantha 

dermis,  while  thorn  branches  Emor>'i' a  Plant  erowins in  arid  resions- 
have  their  origin  in  the  wood  beneath.  They  usually  come 
from  adventitious  buds. 


211.    Stems    as   Tendrils.  —  Stems   are   also   frequently 

met  with  under  the 
form  of  tendrils.  As 
normal  buds  and 
branches  never  grow 
except  from  the  axils 
of  leaves,  this  kind  of 
tendril  can  always  be 
recognized  by  its  posi- 
tion. In  the  grape  and 
Virginia  creeper,  where 


the  leaves  on  alternate 

8ideS        °f       the        Stem' 

they  represent  terminal 
flower  buds  which  have  been   pushed  aside  by  stronger 


148 


THE   STEM   PROPER 


lateral  ones  (Sec.  245).1  The  usurping  bud  continues  the 
growth  of  the  shoot  until  it  is  in  turn  displaced  by  some 
succeeding  lateral  one,  and  so  on,  forming  a  succession  of 
apparently  lateral  tendrils. 

212.  Stems  as  Foliage.  —  When  branches  take  the  place 
of  foliage,  as  they  not  infrequently  do,  they  are  generally 
so  much  disguised  that  it  is  diffi- 
cult to  recognize  them,  but  a 
little  attention  to  their  point  of 
origin  will  usually  make  their 
nature  clear.  The  asparagus  has 
already  been  referred  to  (Sec.  68). 
Still  more  striking  examples  are 
found  in  the  butcher's  broom  of 
Europe  (Riiscus  aculeatus)  and 
the  pretty  little  Myrsiphyllum 
of  the  greenhouses,  wrongly 
called  smilax,  that  is  so  much 
used  for  decoration.  The  green 
blades  of  these  plants,  which  are 
commonly  regarded  as  foliage,  are  not  true  leaves,  but 
curiously  shortened  and  flattened  branches  that  have  taken 
upon  themselves  the  office  of  leaves.  Their  real  nature 
is  shown  by  the  fact  that  they  spring  each  from  the  axil 
of  a  little  scale  or  bract  that  represents  the  true  leaf. 

PRACTICAL  QUESTIONS 

1.  Which  of  the  stems  named  below  are  woody,  and  which  herba- 
ceous, or  suffrutescent  ?     Blackberry,  hollyhock,  pokeweed,  cotton,  okra, 
morning-glory,  asparagus,  garden  sage,  reed,  corn,  wheat,  periwinkle, 
sunflower,  strawberry,  bear's  grass,  broom  straw. 

2.  Why  is  it  that  so  many,  both  of  hot-weather  and  cold-weather 
herbs,  for  example,  knot  weed  (Polygonum  aviculare),  purslane,  spurge, 
carpet  weed  (Mollugo),  winter  chick  weed,  Indian  strawberry,  and  dan- 
delion, all  adopt  the  same  habit  of  clinging  close  to  the  earth  ?     (205.) 

3.  Would  such   a  habit  be   of  any  advantage   to  roadside  weeds 
and  other  herbs  growing  in  exposed  places  where  they  are  liable  to  be 
trodden  upon  and  bitten  by  cattle  ? 

1  See  also  Gray's  "  Structural  Botany,"  page  54,  §  no. 


293.  —  Stem   leaves    (cladophylls) 
of  a  ruscus,  bearing  flowers. 


STEMS    OF   MONOCOTYLEDONS  149 

4.  Is  there  any  difference  in  the  height  of  the  stem  of  a  dandelion 
flower  and  a  dandelion  ball? 

5.  Of  what  advantage  is  this  to  the  plant? 

6.  By  what   means   does  the  gourd  climb?  the  butter  bean?  the 
English  pea?  trumpet  honeysuckle?  grape?  maypop?  smilax?  Virginia 
creeper?  clematis? 

7.  Why  do  we  "stick"  peas  with  brush,  and  hops  with  poles? 

8.  Are  gourds,  watermelons,  squashes,  pumpkins,    etc.,   naturally 
climbing,  or  prostrate? 

9.  Why  does  not  the  gardener  provide  them  with  poles  or  trellises 
to  climb  on? 

10.  Name  some  plants  the  stems  of  which  are  used  as  food. 

1 1 .  Name  some  stems  from  which  useful  articles,  such   as  sugar, 
gums,  and  medicines  are  obtained. 

12.  Do  twining  plants  grow  equally  well  on  horizontal  and  upright 
supports?     (159,  1 60,  244.) 

13.  If  there  is  any  difference,  which  do  they  seem  to  prefer? 


STEMS  OF  MONOCOTYLEDONS 

MATERIAL.  —  A  stem  of  smilax,  asparagus,  or  other  monocotyledon 
that  has  stood  in  red  ink  for  three  to  six  hours.  A  dried  cornstalk ; 
the  handle  of  a  palm-leaf  fan.  (It  would  be  better,  of  course,  to  have 
all  specimens  fresh,  if  possible,  and  for  those  who  live  in  the  southern 
States  fresh  stalks  of  sugar  cane,  palmetto,  or  yucca,  will  afford  admir- 
able objects  for  study.) 

213.  Examination  of  a  Monocotyledonous  Stem. — Take 
one  of  the  dry  cornstalks  that  can  be  found  in  the  fields, 
almost  anywhere,  and  study  its  external  characters.  How 

are  the  internodes  divided   from   one 

,p 

another  ?     What  is  the  use  of  the  very  /     /c       ^ 

firm,  smooth  epidermis  ?  Notice  a 
hollow,  grooved  channel  running  down 
one  side  of  the  joints,  or  internodes ; 
does  it  occur  in  all  of  them  ?  Is  it  on 

.  .,  ...  294.— Cross  section  of 

the  same  side  or  on  opposite  sides  a  staik  of  com :  v,  fibro- 
of  the  alternate  internodes?  Follow  vascular  bundles -,  *,cor- 
one  of  these  grooves  to  the  node  from 
which  it  originates  ;  what  do  you  find  there  ?  (In  a  dried 
stalk  the  bud  will  probably  have  disappeared,  but  traces 
of  it  can  usually  be  found.)  After  studying  the  internal 


ISO 


THE   STEM   PROPER 


„..* 


structure  of  the  stalk  you  will  understand  why  this  groove 
should  occur  on  the  side  of  an  internode  bearing  a  bud 
or  fruit. 

Cut  a  cross  section  midway  between 
two  nodes,  and  observe  the  composition 
of  the  interior;  of  what  does  the  bulk 
of  it  appear  to  consist  ?  Notice  the 
arrangement  of  the  little  dots  like  the 
ends  of  cut-off  threads  that  are  scattered 
through  the  pith ;  where  do  they  appear 
to  be  most  abundant,  toward  the  center 
or  the  circumference  ? 

Make  a  vertical  section  through  one  of 
groove ;   c,  cortex ;    the  nodes.     Cut  a  thin  slice  of  the  pith, 

v,  fibrovascular  bun-     ,     ,,  .  ,      ,.    ,  , 

dies    mingled    with    hold  it  up  to  the  light,  and 
parenchyma;  £,bud;    examine  it  with  a  hand 

n,  node.  .  _ .  ... 

lens.     Observe  that  it  is 
composed   of    a   number   of   tiny  oblong 
compartments   or   cells   packed   together         iRHU 
like  bricks  in  a  wall.     These  are  dry  and         i- 
empty  now,  but  in  the  living  stem  were 
filled  with  nourishing  fluids  consisting  of        lilf 
protoplasm   and    cell    sap   (Sec.    9),    and  'M 

formed  what  is  known  to  botanists  as  the 
parenchyma,  a  word  meaning  parent  tis-    ^f'0T^n\^ol 
sue,  because  from  it  all  the  other  tissues    the  interior  of  a  dry 

i      .        •,  cornstalk  as  seen  un- 

are  derived.  der  the  lens,  showing 

Draw  out  one  of  the  woody  threads  run-    the  cellular  structure 

i_  .       •,  .  ,          T,         ,  of   the   parenchyma : 

nmg  through  the  pith.     Break  away  a  bit    v<  fibrovascular  bun- 
of  the  epidermis  and  see  how  very,  closely    dles  '•    f-    Pith-   or 

,  .       ,  .         .  parenchyma. 

they  are  packed  on  its  inner  surface. 
Trace  the  course  of  the  veins  in  the  bases  of  the  leaves 
that  may  be  found  clinging  to  some  of  the  nodes;  find 
their  point  of  union  with  the  stem ;  with  what  part  of 
it  do  they  appear  to  be  continuous?  Has  this  anything 
to  do  with  the  greater  abundance  of  fibers  near  the  epider- 
mis ?  Can  you  follow  the  fibers  through  the  nodes,  or  do 
they  become  confused  and  intermixed  with  other  threads 


STEMS   OF   MONOCOTYLEDONS  151 

there  ?  (If  sugar  cane  is  used  for  this  study,  the  ring  of 
scars  left  by  the  vascular  bundles  as  they  pass  from  the 
leaves  into  the  stem  will  be  seen  beautifully  marked  just 
above  the  nodes.) 

If  there  is  an  eye  or  bud  at  the  node,  look  and  see  if 
any  of  the  threads  go  into  it.  Can  you  account  now  for 
the  depression  that  occurs  in  the  internode  above  the  eye 
or  bud  ? 

Make  drawings  of  both  cross  and  vertical  sections  show- 
ing the  points  brought  out  in  your  examination  of  the  corn- 
stalk. 

214.  The  Vascular  System.  —  To  find  out  the  use  of 
the  threads  that  you  have  been  tracing,  examine  a  piece 
of  a  living  stem  of  wild  smilax  or  other  monocotyledon 
that  has  stood  in  red  ink  for  three  to  twenty-four  hours. 
(If  the  specimen  stands  in  the  coloring  fluid  too  long  the 
dye  will  gradually  percolate  through  all  parts  of  it.      If 
this  should  be  the  case,  look  for  the  lines  that  show  the 
ink  most  plainly.)      Notice  the  course  the  coloring  fluid 
has  taken ;   what  would   you  infer    from   this  as  to  the 
office  of  the  woody  fibers  ? 

These  threads  constitute  what  is  called  the  vascular 
system  of  the  stem,  because  they  are  made  up,  to  a  large 
extent,  of  little  vessels  or  ducts,  along  which  the  sap  is 
conveyed  from  the  roots  to  the  leaves  and  back  from  the 
leaves  to  the  root  and  stem  after  it  has  been  elaborated  into 
food.  They  are,  so  to  speak,  the  water  pipes  that  supply 
the  leaf  community  with  the  liquid  nourishment  which  it 
works  up  into  food  during  the  process  of  photosyn- 
thesis (Sec.  24). 

215.  The  Stem  as  a  Water  Carrier.  — We  see  from  this, 
that  the  stem,  besides  serving  as  a  mechanical  support, 
is  the  natural  line  of   communication  between  the  roots, 
where  the  raw  material  for  feeding  the  plant  is  gathered, 
and  the  leaves,  where  this  material  is  manufactured  into 
food.     After  the  sap  is  there  elaborated  and  the  surplus 
moisture  given  off  by  transpiration,   the  nourishment  is 


152 


THE   STEM   PROPER 


returned  to  be  distributed  to  the  other  organs.  Even  the 
roots  can  not  be  fed  by  the  liquid  they  absorb  from  the  soil 
until  it  has  been  elaborated  in  the  leaves,  just  as  our 
bodies  can  not  be  sustained  by  what  we  eat  and  drink  until 
it  has  been  digested  in  our  stomachs.  Hence,  if  the  leaves 
of  a  tree  are  diseased  or  destroyed  by  ignorant  pruning, 
the  roots  will  suffer  and  die  just  as  the  leaves  do  if  the 
roots  are  injured. 

On  account  of  this  double  line  of  communication  which 
they  have  to  maintain,  the  vascular  threads,  or  bundles,  as 
they  are  technically  called,  are  double;  one  set,  composed 
of  larger  ducts,  carrying  water  up,  and  another  set  of 
smaller  ones  bringing  back  the  digested  food.  Can  you 
give  a  reason  for  their  difference  in  size  ? 

216.  Woody  Monocotyledons.  —  Examine  sections  of 
yucca,  smilax,  or  of  palmetto  from  the  handle  of  a  fan, 
and  compare  them  with  your  sketches  of  the  cornstalk. 
In  which  are  the  vascular  fibers  most  abundant  ?  Which 
is  the  toughest  and  strongest  ?  Why  ?  Trace  the  course 
of  the  leaf  fibers  from  the  point  of  insertion  to  the 
interior.  How  does  it  differ  from  that 
of  the  fibers  in  a  cornstalk  ? 

217.  Growth  of  Monocotyledonous 
Stems.  —  Refer  to  the  experiment  in  Sec- 
tion 43  ;  refer  also  to  what  has  just  been 
learned  regarding  the  course  of  the  leaf 
veins  at  the  nodes  of  the  cornstalk  (Sec. 
213),  and  you  will  have  no  difficulty  in 
identifying  these  veins  as  part  of  the  vas- 
cular system.  Each  successive  leaf  sends 
its  vascular  bundles  down  into  the  main 
system  of  the  stem,  and  any  increase 
297.  — Longitudinal  in  the  diameter  of  monocotyledons  takes 
section  through  the  p]ace  by  the  intercalation  of  new  bundles 

stem  of  a  palm,  show-  * 

ing  the  curved  course    from  the  leaves  as  they  develop  at  the 

Idt  (G™^  nodes  above'  In  J°inted  ste™  like  the 
FALKENBERG).  corn  and  sugar  cane  and  other  grasses, 


STEMS   OF  MONOCOTYLEDONS 


153 


this  intercalation  takes  place,  as  we  have  seen  (Sec.  213), 
at  the  nodes,  forming  the  hard  rings  known  as  joints,  but 
in  other  monocotyledons  the  fibers  entering  the  stem  from 
the  leaves  generally  tend  first  downwards,  towards  the 
interior  (Fig.  297),  then  bend  outward  toward  the  sur- 
face, where  they  become  entwined  with 
others  and  form  the  tough,  inseparable 
cortex  that  gives  to  palmetto  and  bamboo 
stems  their  great  strength. 

This  addition  of  fresh  vascular  bundles 
as  the  axis  lengthens  will  explain  why  the 
lower  joints  of  cornstalks  and  sugar  cane 
are  so  much  more  hard  and  woody  than  the 
upper  ones.  Generally,  however,  mono- 
cotyledonous  stems  do  not  increase  in  diam- 
eter after  a  certain  point,  and  as  they  can 
contain  only  a  limited  number  of  vascular 
fibers,  they  are  incapable  of  supporting  an 
extended  system  of  leaves  and  branches. 
Hence  this  class  of  plants,  with  a  few  trunk  of  monocoty- 
exceptions,  like  smilax  and  asparagus,  are  1( 
characterized  by  simple,  columnar  stems,  and  a  limited 
spread  of  leaves.  The  cabbage  palmetto,  banana,  and 
Spanish  bayonet  (  Yucca  aloifolia)  are  familiar  examples  in 
the  warmer  parts  of  our  country. 

CQ}     Strength    of    the    Monocotyledonous  Structure.  — 

Stems  of  this  class  are  admirably  adapted  by  their  struc- 
ture to  the  purposes  of  mechanical  support.  It  is  a  well- 
known  law  of  mechanics  that  a  hollow  cylinder  is  a  great 
deal  stronger  than  the  same  mass  would  be  in  solid  form, 
as  may  easily  be  tested  by  the  simple  experiment  of  break- 
ing in  your  fingers  a  cedar  pencil  and  a  joint  of  cane 
or  a  stem  of  smilax  of  the  same  weight.  In  stems  that 
may  be  technically  classed  as  solid  in  structure,  like 
the  corn  and  palmetto,  the  interior  is  so  light  compared 
with  the  hard  epidermis  that  the  result  is  practically  a 
hollow  cylinder. 


154 


THE   STEM    PROPER 


PRACTICAL   QUESTIONS 


1 .  Old  Fort  Moultrie  near  Charleston  was  built  originally  of  pal- 
metto logs ;  was  this  good  engineering  or  not?     Why? 

2.  Why  is  a  stalk  of  sugar  cane  so  much  heavier  than  one  of  corn? 
A  green  cornstalk  than  a  dead  one?     (215.) 

3.  Explain  the  advantages  of  structure  in  a  culm  of  wheat;  a  stalk 
of  corn;  a  reed.     (218.) 

4.  Would  the  same  quality  be  of  advantage  to  an  oak  ?     Why,  or 
why  not? 

5.  Is  it  any  advantage  to  the  farmer  that  grain  straw  is  so  light? 

STEMS   OF   DICOTYLEDONS 

MATERIAL.  —  Twigs  from  one  to  three  years  old  of  almost  any  kind 
of  hard  wood  shoots  ;  elm,  basswood,  mulberry,  leatherwood,  and  paw- 
paw show  the  bast  well  ;  sassafras,  slippery  elm,  birthwort  {Aristolo- 
ckia),  and  in  spring,  hickory  and  willow,  show  the  cambium  ;  grape 
and  Trumpet  vine  the  ducts.  Have  some  twigs  placed  in  red  ink  from 
four  to  twelve  hours  before  the  lesson  begins.  Grape,  peach,  or  hickory 
will  answer  well  for  this  purpose. 

219.    Examination   of   a  Typical   Specimen.  —  Examine 
carefully  the  outer  surface  of  a  young  twig,  not  less  than 
one  nor  more  than  three  years  old,  of  any 
convenient  specimen.      Notice  the  scars  left 
by  the  leaves  of  the  season  as  they  fell  away, 
and  look  for  one  or  more   little  roundish 
dots  called  leaf  traces,  that  mark  the  points 
where  the  fibrovascular   bundles  from   the 
leaf  veins  passed  into  the  stem.     The  little 
oblong  or  lens  shaped  corky  spots  that  dot 
the  surface  of  a  twig  are  called  lenticels. 
They  are  the  breathing  pores  or  ventilators 
through  which   the    air   penetrates    to    the 
299.— Alternate    inner    parts    of    the    stem.      They   usually 
LTTtrmTnS    disaPPear    on    older    branches,    where    the 
bud;  j.j,  leaf  scars;    outer  bark  is  constantly  breaking  away  and 
lenlkds'.^651  l'1'    sloughing   off.      Sometimes,  however,  they 
are  quite  persistent,  as  in  the  peach,  cherry, 
and  china  tree.     The  characteristic  markings. of  the  birch 
bark,  which  make  it  so  ornamental,  are  due  to  the  lenti- 


STEMS    OF   DICOTYLEDONS  155 

eels.  As  the  tree  grows  they  elongate  either  vertically, 
by  the  lengthening  of  the  twig,  or  horizontally,  by  its 
increase  in  diameter,  until  they  often  appear  as  long  slits. 

Scrape  off  a  little  of  the  brownish,  or  sometimes  almost 
colorless  outer  covering.  This  is  the  epidermis,  and  is 
replaced  by  the  outer  corky  layer  of  the  bark  in  older 
stems.  As  the  stem  increases  in  diameter  from  year  to 
year  this  outer  covering  is  broken  up  and  pushed  aside  to 
make  way  for  the  new  growth,  so  that  the  bark  is  con- 
stantly dying  and  sloughing  off  from  the  outside  and  as 
constantly  renewed  from  within.  Under  the  epidermis, 
notice  a  greenish  layer  of  young  bark  ;  beneath  this  a  layer 
of  rather  tough,  stringy  fibers  called  bast,  and  finally  a 
harder  woody  substance  that  constitutes  the  bulk  of  the 
interior  of  the  stem.  Cut  through  this  to  the  very  center 
of  the  axis  and  we  find  a  cylinder  of  lighter,  pithy  texture; 
this  is  the  same  as  the  parenchyma  or  parent  tissue  that 
we  found  pervading  the  interior  of  the  cornstalk  (Sec.  213). 
It  is  usually  called  the  pith  or  medulla,  and  is  the  only  part 
present  in  very  young  stems. 

Between  the  woody  axis  and  the  bark  is  a  more  or  less 
soft  and  juicy  ring  called 

220.  The  Cambium  Layer.  —  This  is  not  always  easily 
distinguishable  with  a  hand  lens,  but  is  conspicuous  in  the 
stems  of  sassafras,  slippery  elm,  aristolochia,  etc.  If  some 
of  these  can  not  be  obtained,  the  presence  of  the  cambium 
can  be  recognized  by  observing  the  tendency  of  most  stems 
to  "  bleed  "  when  cut,  between  the  wood  and  bark.  This 
is  because  the  cambium  is  the  active  part  of  the  stem  in 
which  growth  is  taking  place,  and  consequently  it  is  most 
abundantly  supplied  with  sap.  This  is  especially  the  case 
in  spring,  when  it  becomes  so  gorged  with  nourishment 
that  if  a  rod  of  hickory  or  elder  is  pounded,  the  pulpy 
cambium  is  broken  up  and  the  bark  may  be  slipped  off 
whole  from  the  wood.  It  is  the  nourishment  contained  in 
the  cambium  of  certain  plants  that  tempts  goats  and  calves 
to  bark  them  in  spring,  and  that  enables  savages,  in  time 


1 56 


THE   STEM   PROPER 


of  dearth,  to  subsist  for  a  while  on  the  buds   and  bark 

of  trees. 

221.  Difference  between 
Dicotyledons  and  Monocoty- 
ledons. —  Cut  cross  and 
vertical  sections  of  your 
specimen,  and  sketch  them 
as  seen  under  the  lens, 
labeling  the  different  parts 
that  have  been  examined. 

300.-Sec«ion  across   a  young  twig  of  Refer   to    Figures    3OO   and 

box  elder,  showing  the  four  stem  regions :  30 1    jf    you    have    any  diffi- 
e,   epidermis,    represented    bv    the    heavy  ,         .        j  •      •  •    i_  •          ^u 

bounding  line;  ^cortex;  w.  vascular  cylin-  Culty  in   distinguishing  the 

der;  /.  pith.     (From  COULTER'S  "  Plant  parts.         Notice     the     little 
Relations.")  .  .  ,  , 

pores  or  cavities  that  dot 

the  woody  part  in  the  cross  section  ;  where  are  they  largest 
and  most  abundant  ?  How  are  the  rings  marked  off  from 
one  another  ?  These  pores  are  sections  of  the  ducts  already 
alluded  to  (Sees.  214, 
215).  They  are  very 
large  in  the  grape  vine, 
and  a  cutting  two  or 
three  years  old  will  show 
them  distinctly.  Exam- 
ine cross  and  vertical 
sections  of  a  twig  that 
has  stood  in  red  ink 
from  three  to  twelve 
hours  and  observe  the 
course  the  fluid  has 
taken.  (The  rapidity 


771 


3oi.  — Section  across  a  twig  of  box  elder 
three  years  old,  showing  three  annual  growth 


with     which     the     liquid     rings,  in  the  vascular  cylinder.    The  radiating 

IS    absorbed   varies   with     HneS  (w)-which  cross  the  vascular  region  (a/), 
represent  the  pith  rays,  the  principal  ones  ex- 
different    Stems     and     at     tending  from  the  pith  to  the  cortex  (c).    (From 

different  seasons.     It  is    ( 

most  rapid  in  spring  and   slower   in  winter.      In   grape, 

plum,  and  peach  it  ascends  quickly.)     What  should  you 


STEMS   OF   DICOTYLEDONS  157 

infer  from  this  as  to  the  office  of  the  ducts  ?  How  does 
this  conclusion  compare  with  your  observations  on  the 
vascular  bundles  of  monocotyledonous  stems  ?  Notice 
that  the  dicotyledon  differs  from  monocotyledonous  stems 
in  having  the  pith  all  gathered  in  a  narrow  cylinder  in  the 
center,  and  the  vascular  tissue  arranged  in  one  or  more 
concentric  layers  around  it,  according  to  the  age  of  the 
stem.  In  general,  dicotyl  stems  may  be  said  to  include 
four  regions;  ist,  the  epidermis  or  bark,  e  (Fig.  300); 
2d,  the  cortex,  c,  made  up  of  the  cambium  and  bast,  with 
certain  other  tissues ;  3d,  the  vascular  cylinder,  or  woody 
portion  w,  made  up  of  concentric  rings  each  representing 
a  year's  growth ;  and  4th,  the  pith  /,  medulla,  or  paren- 
chyma, as  it  is  variously  termed  by  botanists, 

222.  Medullary  Rays. — Observe  the  whitish  silvery  lines 
that  radiate  in  every  direction  from  the  center,  like   the 
spokes  of  a  wheel  from  the  hub.     These  are  the  medullary 
rays  and  consist  of  threads  of  pith  that  serve  as  lines  of 
communication  between  the  "parent  tissue"  and  the  grow- 
ing cambium   layer.     In  old  stems  the   central   pith  fre- 
quently disappears  and  its  office  is  filled  by  the  medullary 
rays,  which  become  quite  conspicuous. 

223.  The   Rings,    into   which    the   vascular   cylinder  is 
divided,  mark  the  yearly  additions  to  the  growth  of  the 
stem,  which  increases  by  the  constant  addition  of   fibro- 
vascular  bundles  from  the  outside ;  hence  such  stems  are 
called   exogens   or    "outside   growers." 

224.  The  Structure  of  the  Fibro- 
vascular  Bundles  is  somewhat  com- 
plicated and  can  not  be  studied  to 
advantage  without  the  aid  of  a  com- 
pound microscope,  but  a  little  atten- 
tion  to   the   diagrams  will    make   it 

•    «.    11-    -LI  T-L       •  f  i  302.— Transverse  section 

intelligible.  The  inner  part  of  each  of  vascu]ar  bundle  from 
bundle  (i.e.,  the  part  toward  the  axis)  stem  of  a  dicotyledon:  /, 

j  r  j      /-i  i  bast;  c,  cambium;  v,  ducts, 

is  made  up  of  woody  fibers  shown  at    w>  wood  cens. 


158 


THE   STEM   PROPER 


w(Fig.  302),  intermingled  with  larger  sized  tubes  or  ducts, 
v,  the  sections  of  which  made  the  pores  referred  to  in 
Section  221.  In  front  of  these  is  the  cambium  layer,  c,  and 

beyond  that,  the  soft  bast 
and  other  tissues  in  which 
elaborated  food  is  being 
brought  down  from  the 
leaves  and  material  for 
growth  provided.  In  very 
young  stems  the  vascular 
bundles  are  separate  and 
distinct,  as  in  Figure  303, 
being  connected  only  by 
a  ring  of  cambium,  but 
as  growth  advances  and 

303.-TransverSesection0fastemofbur-  "lore  bundles  are  formed 
dock,  showing  fibrovascular  bundles  not  to  supply  the  new  buds 
completely  united  into  a  ring.  ,  ,  r  ,  ,  , 

and  leaves  of  the  devel- 
oping axis,  they  become  crowded  into  a  ring  (Fig.  304), 
which  is  separated  into  woody  wedges  by  the  threads  of 
pith  (medullary  rays)  that  run  between  them  from  the 
center  to  the  cortex.  The  cambium  constantly  advances 
outwards,  beginning  every  spring  a  new  season's  growth 
and  leaving  behind  the  ring  of  ducts 
and  woody  fibers  made  the  year  before. 
As  the  work  of  the  plant  is  most  active 
and  its  growth  most  vigorous  in  spring, 
the  largest  ducts  are  formed  then,  the 
tissue  becoming  closer  and  finer  as 
the  season  advances,  thus  causing  the 
division  into  annual  rings  that  is  so 
characteristic  of  dicotyl  stems.  Each  older  dicotyf stem,  show- 
new  stratum  of  growth  is  made  up  of 
the  fibrovascular  bundles  that  supply 
the  leaves  and  buds  and  branches  of  the  season.  Fig- 
ure 305  gives  a  diagrammatic  section  illustrating  the 
passage  of  the  bundles  from  the  leaves  to  the  stem  of  a 
dicotyledon,  each  successive  node  sending  down  its  quota. 


304.  —  Diagram    of    an 


STEMS   OF   DICOTYLEDONS 


159 


In   this  way  we  see  that  the  increase  of  dicotyl  trunks 
and  branches  is  approximately  in  an  elongated  cone  (Fig. 

306),  the  number  of 
rings  gradually  diminish- 
ing toward  the  top  till  at 
the  terminal  bud  of  each 
bough  it  is  reduced  to 


305.  —  Diagrammatic  view  of  a  leafy  stem 
of  clematis,  showing  the  arrangement  of  the 
fibrovascular  bundles:  a,  b,  c,  —e,f,  d,  the 
fascicles  from  the  lower  pair  of  leaves;  i, g, 
I,  —k,  h,  m,  the  fascicles  from  the  second 
pair  of  leaves ;  q,  r,  s,  —p,  n,  o,  the  fascicles 
from  the  third  pair  of  leaves ;  x,  t,  fascicles 
of  the  fourth  pair  of  leaves ;  f}.  a,  —  y,  S,  pairs 
of  undeveloped  leaves  not  as  yet  having 
fascicles  (GRAY,  after  NAGELI). 


306.  —  Diagram  illustrating  the  an- 
nual growth  of  dicotyledons. 


a  single  one,  as  in   the 
stems  of  annuals. 

Sometimes  a  late  au- 
tumn, succeeding  a  very 
dry  summer,  will  cause  trees  to  take  on  a  second  growth, 
and  thus  form  two  layers  of  wood  in  a  single  season,  so 
we  can  not  always  rely  absolutely  upon  the  number  of 
rings  in  estimating  the  age  of  a  tree. 

225.  The  Stems  of  Conifers.  —  Examine  a  young  stem 
of  pine,  and  compare  with  the  one  just  studied.  What 
difference  do  you  notice  ?  This  absence  of  the  duct  pores 
constitutes  one  of  the  most  conspicuous  differences  be- 
tween the  stems  of  conifers  (cone  bearers)  and  dicotyledons. 


j6o  THE   STEM   PROPER 

The  ducts  are  there,  but  they  are  formed  differently  from 
those  of  other  exogens,  and  can  not  be  studied  without  a 
compound  microscope.  From  what  part  of  the  stem  does 
the  rosin  exude?  Place  a  cutting  in  red  ink  and  notice 
through  what  part  the  fluid  rises ;  where,  would  you  judge 
from  this,  is  the  most  active  part  of  the  stem  ? 

PRACTICAL  QUESTIONS 

1 .  Explain  the  principle  upon  which  boys  slip  the  bark  from  certain 
kinds  of  wood  in  spring  to  make  whistles.     (220.) 

2.  Why  can  not  they  do  this  in  autumn  or  winter? 

3.  Name  some  of  the  plants  commonly  used  for  this  purpose. 

4.  Is  the  spring,  after  the  buds  begin  to  swell,  a  good  time  to  prune 
fruit  trees  and  hedges?     Why?     (220.) 

5.  What  is  the  best  time,  and  why? 

6.  Why  are  grape  vines  liable  to  bleed  to  death  if  pruned  too  late  in 
spring?     (220,221.) 

7.  Why  are  nurserymen,  in  grafting,  so  careful  to  make  the  cambium 
layer  of  the  graft  hit  that  of  the  stock?     (220.) 

8.  In  calculating  the  age  of  a  tree  or  bough  from  the  rings  of  annual 
growth  should  we  take  a  section  from  near  the  tip,  or  the  base?     Why? 
(224.) 

MOVEMENT  OF  WATER   THROUGH  THE   STEM 

MATERIAL.  —  An  egg,  a  small  cup,  and  some  salt  water.  A  potted 
young  plant  of  corn,  calla  lily,  tropaeolum,  sunflower,  etc.  A  few  centi- 
meters each  of  glass  tubing  and  rubber  tubing  about  the  diameter  of  the 
stem  of  the  plant.  A  twig  of  willow,  currant,  or  other  easily  rooting 
shrub. 

226.  Difficulty  of  Accounting  for  Sap  Movement. — Just 
what  causes  the  rise  of  sap  in  the  stem  is  one  of  the 
puzzles  of  vegetable  physiology  that  botanists  have  not 
yet  been  able  to  solve  completely.  It  is  closely  connected 
with  the  phenomena  of  transpiration,  the  rapidity  of  the 
current  increasing  and  decreasing  according  to  the  activity 
of  the  evaporating  surfaces.  If  loss  of  water  begins  at  any 
spot  through  growth  or  transpiration,  the  nearest  tissues 
give  up  their  water  first,  then  the  more  remote,  and  so  on, 
till  the  most  distant  —  generally  the  roots  —  have  to  absorb 
water  from  without,  and  thus  a  constant  current  is  kept  up 
toward  the  places  where  moisture  is  needed. 


MOVEMENT  OF  WATER  THROUGH  THE  STEM  161 

227.  Osmose.  —  The  rise  of  sap  is  partly  due  to  the  pres- 
sure caused  by  the  constant  absorption  of  soil  water  through 
the  absorbent  hairs  of  the  root.  The  passage  of  liquids 
through  the  walls  of  cells  and  tissues  is  known  as  osmose 
and  takes  place  when  liquids  of  different  densities  are 
separated  by  a  thin  membrane,  the  principle  governing 
the  direction  of  the  flow  being  that  the  thinner,  lighter 
liquid  passes  toward  the  denser.  The  nature  of  the  sub- 
stances, also,  must  be  considered  ;  those  that  are  crystalline 
and  easily  soluble,  like  sugar  and  salt,  pass  readily  through 
membranes,  while  gelatinous  ones  pass  with  difficulty  or  not 
at  all. 

Chip  away  a  bit  of  the  shell  from  the  big  end  of  an  egg, 
taking  care  not  to  injure  the  thin  membrane  underneath. 
Make  a  small  puncture  through  both  shell  and  membrane 
in  the  small  end  and  place  the  egg  in  a  cup  with  its  big 
end  in  salt  water.  In  a  few  hours  the  contents  will  be  found 
running  out  of  the  puncture  at  the  other  end,  having  been 
forced  out  by  the  water  that  made  its  way  in  below.  And 
there  are  no  pores  visible,  even  with  the  most  powerful 
microscope,  in  the  membrane  that  lines  the  eggshell. 

The  same  principle  is  well  illustrated  by  the  experiment 
described  in  Section  204,  the  water  passing  by  osmose 
through  the  walls  of  the  cells  that  make  up  the  substance 
of  the  stem.  Take  one  of  the  stem  sections  after  it  has 
lain  in  fresh  water,  and  transfer  it  to  a  five  per  cent  solution 
of  salt  water  (about  a  tablespoonful  of  salt  to  a  tumbler 
of  liquid).  Allow  it  to  remain  as  before,  and  then  exam- 
ine. It  will  be  found  to  have  become  straight  again,  or 
perhaps  even  to  have  coiled  over  in  the  opposite  direction. 
This  is  because  the  thinner  liquid  of  the  cells  has  passed 
out  by  osmose  into  the  thicker  salt  solution,  so  that  the 
interior  cells  have  become  flabby,  while  the  exterior  ones, 
protected  by  the  epidermis,  remain  distended  and  thus 
cause  the  section  to  curve  inward. 

The  passage  of  liquids  into  a  sac  or  cell  is  called  endos- 
mose,  out  of  it,  exosmose.  Which  is  it  that  takes  place 
between  the  soil  water  and  the  root  ? 

ANDREWS'S   EOT.  —  1 1 


162  THE   STEM   PROPER 

228.  Action  of  Osmose  in  the  Root.  — The  sap  within  the 
root  is  generally  denser  than  the  water  of  the  soil,  so  there 
is  a  continuous  osmotic  flow  from  the  latter  to  the  former, 
but  within  the  stem  the  fluid  is  more  nearly  of  the  same 
density  throughout  and  the  conditions  for  osmosis  are  not 
so  favorable,  though  it  probably  does  take  place  to  some 
extent.     A  more  efficient  cause  is  generally  held  to  be  the 
force  exerted  by  the  upward  pressure  of  water  absorbed 
into  the  roots,  and  known  as 

229.  Root  Pressure.  —  Cover  a  calla  lily,  young  corn- 
stalk, sunflower,  or  other  succulent  herb  with  a  cap  of 
oiled  paper  to  prevent  transpiration,  set  the  pot  containing 
it  in  a  pan  of  warm  water  and  keep  it  at  a  gentle  heat. 
After  a  few  hours  look  for  water  drops  on  the   leaves. 
Where  did  this  water  come  from  ?     How  did  it  get  up 
into  the  leaves  ? 

Now  cut  off  the  stem  of  the  plant  six  or  eight  centimeters 
(three  or  four  inches)  from  the  base.  Slip  over  the  part 
remaining  in  the  soil  a  bit  of  rubber  tubing  of  about  the 
same  diameter  as  the  stem,  and  tie  tightly  just  below  the 
cut.  Pour  in  a  little  water  to  keep  the  stem  moist,  and 
slip  in  above  a  short  piece  of  tightly  fitting  glass  tubing. 
Watch  the  tube  for  several  days  and  note  the  rise  of  water 
in  it.  The  same  phenomenon  may  be  observed  in  the 
"  bleeding "  of  rapidly  growing,  absorbent  young  shoots, 
such  as  grape,  sunflower,  gourd,  tobacco,  etc.,  if  cut  off 
near  the  ground  in  spring  when  the  earth  is  warm  and 
moist.  This  flow  can  not  be  due  to  transpiration,  since 
the  leaves  and  other  transpiring  parts  have  been  removed. 
Transpiration,  by  causing  a  deficiency  of  moisture  in  cer- 
tain places  may  influence  the  direction  and  rapidity  of  the 
current,  but  does  not  furnish  the  motive  power,  which 
evidently  comes,  in  part  at  least,  from  the  roots,  and  is 
the  expression  of  their  absorbent  activity. 

230.  Root  Pressure  and  Root  Pull. — There  is  no  antag- 
onism between  these  two  forces.     Root  pull   affects   the 
body  of  the  plant  with  its  system  of  tubes  and  cells ;  root 


MOVEMENT  OF  WATER  THROUGH  THE  STEM   163 


pressure  affects  the  free  contents  of  these  parts,  just  as 
we  may  sink  a  water  pipe  into  the  ground  and  at  the  same 
time  force  the  water  upward  through  it. 

231.  Direction  of  the  Current.  —  Remove  a  ring  of  the 
cortical  layer  from  a  twig  of  any  readily  rooting  dicoty- 
ledon, being  careful  to  leave  the  woody 

part  with  the  cambium  intact  Place 
the  end  below  the  cut  ring  in  water,  as 
shown  in  Figure  307.  The  leaves  above 
the  girdle  will  remain  fresh.  How  is 
the  water  carried  to  them  ?  How  does 
this  agree  with  the  movement  of  red  ink 
observed  in  Section  221  ? 

Next  prune  away  the  leaves  and  pro- 
tect the  girdled  surface  with  tin  foil,  or 
insert  it  below  the  neck  of  a  deep  bottle 
to  prevent  evaporation  and  wait  until 
roots  develop.  Do  they  come  most  abun- 
dantly from  above  or  below  the  decorti-  had  been  kepf  stand- 

,     ,      .         ,  ing  in  water  after  the 

cated  ring  ?  removal  of  a  ring  of 

These  experiments  show  that  the  up-    cortical  tissue:  a,  level 

,  ...  ,     /         of  the  water;  ^swell- 

Ward  movement  of  crude  sap  toward  the    jng    formed    at    the 

leaves   is   mainly  through    the   ducts   in    uPPer  denudation;  c, 
the  woody  portion  of  the  stem,  while  the 
downward  flow  of  elaborated  sap  from  the  leaves  takes 
place   chiefly   through    the    soft   bast   and   certain   other 
vessels  of  the  cortical  layer. 

232.  Ringing  Fruit  Trees.  —  This  explains  why  farmers 
sometimes  hasten  the  ripening  of  fruit  by  the  practice  of 
ringing.     As  the   food   material   cannot   pass   below  the 
denuded  ring,  the  parts  above  become  gorged  and  a  pro- 
cess of   forcing  takes  place.      The   practice,  however,  is 
not  to  be  commended,  except  in  rare  cases,  as  it  generally 
leads  to  the  death  of  the  ringed  stem.     The  portion  below 
the  ring  can  receive  no  nourishment  from  above,  and  will 
gradually  be  so  starved  that  it  can  not  even  act  as  a  carrier 
of  crude  sap  to  the  leaves,  and  so  the  whole  bough  will 


THE   STEM   PROPER 


perish.     Figure  308  will  give  a  good  general  idea  of  the 
movement    of    sap    in    trees,    the 
arrows  indicating  the  direction  of 
„—    the    movement    of    the    different 
substances. 

233.  Sap  Movement  not  Circula- 
tion.—  It  must  not  be  supposed 
that  this  flow  of  sap  in  plants  is 
analogous  to  the  circulation  of  the 
blood  in  animals,  though  frequently 
spoken  of  in  popular  language 
as  the  "  circulation  of  the  sap." 
There  is  no  central  organ  like  the 
heart  to  regulate  its  flow,  and  the 
water  taken  up  by  the  roots  does 
not  make  a  continual  circuit  of 

308. -Diagram    showing   gen-     the    plant   body  as   the    blood    does 
eral  movement  of  sap.  .      , .  ,    , 

of  ours,  but  is  dispersed  by  a  pro- 
cess of  general  diffusion,  part  into  the  air  through  tran- 
spiration, and  part  through  the  plant  body  as  food, 
wherever  it  is  needed. 

234.  Unexplained  Phenomena.  —  While  root  pressure  will 
account  for  the  rise  of  sap  to  a  certain  extent,  none  of  the 
causes  assigned  by  physiologists  are  sufficient  to  explain  all 
the  phenomena.  The  highest  force  as  yet  proved  to  be 
exerted  by  it  is  sufficient  to  balance  a  column  of  water 
only  ten  to  fifteen  meters  (thirty  to  fifty  feet)  high.  The 
power  with  which  it  acts  seems  to  vary  in  different  plants. 
In  the  nettle  it  is  capable  of  lifting  the  sap  to  a  height  of 
about  4.5  meters  (15  feet)  and  in  the  grapevine  more  than 
ii  meters,  or  about  36.5  feet.  It  is  claimed  that  in  the 
birch  it  exerts  a  lifting  force  nearly  equal  to  the  pressure 
of  a  column  of  water  eighty-five  feet  high,  but  even  this  is 
quite  inadequate  to  explain  the  rise  of  sap  to  the  tops  of 
trees  three  hundred  and  four  hundred  feet  high,  like  the 
giant  redwoods  of  California  or  the  still  taller  blue  gums  of 
Australia.  Capillary  attraction  and  the  buoyant  force  of 


MOVEMENT  OF  WATER  THROUGH  THE  STEM   165 

air  bubbles  in  the  cavities  of  the  stem,  in  conjunction  with 
various  other  causes,  have  been  called  in  to  explain  the 
phenomenon,  but  so  far  as  our  knowledge  goes  at  present 
none  of  them  seems  to  account  for  it  satisfactorily. 

PRACTICAL  QUESTIONS 

1.  In  pruning,  why  should  the  cutting  be  confined  as  far  as  possible 
to  young  shoots? 

2.  Why  should  vertical  shoots  be  cut  off  obliquely? 

3.  Why  should  pruning  not  be  done  in  wet  weather? 

4.  Why  will  a  leafy  shoot  heal  more  quickly  than  a  bare  one? 
(24,  25,  26,  200.) 

5 .  Why  does  a  transverse  cut  heal  more  slowly  than  a  vertical  one  ? 
(231-  232.) 

6.  Why  does  a  ragged  cut  heal  less  readily  than  a  smooth  one  ? 

7.  Why  does  the  formation  of  wood  proceed  more  rapidly  as  the 
amount  of  transpiration  is  increased  ?     (226.) 

8.  Wrhy  do  nurserymen  sometimes  split  the  cortex  of  young  trees 
in  summer  to  promote  the  formation  of  wood?     (219.) 

9.  What  is  the  advantage  of  scraping  the  stems  of  trees? 

10.  Explain  the  frothy  exudations  that  often  appear  at  the  cut  ends 
of  firewood,  and  the  singing  noise  that  accompanies  it.  (215,  224.) 

u.  What  advantage  is  it  to  high  climbing  plants,  like  grape  and 
trumpet  vine  (Tecoma),  to  have  such  large  ducts?  (214,  215,  221.) 

12.  Why  is  the  process  of  layering  more  apt  to  be  successful  if  the 
shoot  is  bent  or  twisted  at  the  point  where  it  is  desired  to  make  it  root  ? 

13.  Why  do  oranges  become  dry  and  spongy  if  allowed  to  hang  on 
the  tree  too  long?    (215,231,232.) 

14.  Why  will  corn  and  fodder  be  so  much  richer  in  nourishment  if, 
instead  of  pulling  the  fodder  when  it  is  mature  and  leaving  the  ears  to 
ripen  in  the  field,  we  cut  down  the  whole  stalk  and  allow  both  fodder 
and  grain  to  mature  upon  it?     (215,  231,  233.) 

15.  Why  will  inserting  the  end  of  a  wilted  twig  in  warm  water  some- 
times cause  it  to  revive?    (229.) 

1 6.  Why  should  we  protect  the  south  side  rather  than   the  north 
side  of  tree  trunks  in  winter? 

17.  Why  does  cotton  run  all  to  weed  in  very  wet  weather? 

1 8.  Why  in  pruning  a  branch  is  it  best  to  make  the  cut  just  above  a 
bud? 

19.  Why  is  the  rim  of  new  bark  or  callus  that  forms  on  the  upper 
side  of  a  horizontal  wound  thicker  than  that  on  the  lower  side?     (231.) 

20.  Why  is   it   that   the  medicinal   or  other  special  properties  of 
plants  are  found  mostly  in  the  leaves  and  bark,  or  parts  immediately 
under  the  bark?     (220,  231.) 


THE   STEM   PROPER 


WOOD   STRUCTURE 

MATERIAL.  —  Select  from  the  billets  of  wood  cut  for  the  fire, 
sticks  of  various  kinds  ;  hickory,  ash,  oak,  chestnut,  maple,  walnut, 
cherry,  pine,  cedar,  tulip  tree,  all  make  good  specimens.  Red  oak 
shows  the  medullary  rays  particularly  well.  Get  sticks  of  green  wood 
if  possible  and  have  them  planed  smooth  at  the  ends.  It  would  be 
well  for  the  teacher  to  have  a  hatchet  and  let  the  class  collect  their 
own  specimens.  Collect  also,  where  they  can  be  obtained,  waste  bits  of 
dressed  lumber  from  a  carpenter  or  joiner.  For  city  schools  prepared 
samples  should  be  obtained  of  the  dealers.  If  nothing  better  is  avail- 
able, any  pieces  of  unpainted  woodwork  about  the  schoolroom  will 
furnish  subjects  for  study. 


309.  —  Cross  section  through  a  black  oak,  showing  heartwood  and  sapwood 
(from  PlNCHOT,  U.S.  Dept.  of  Agr.). 

235.  Detailed  Structure  of  a  Woody  Stem.  —  Select  a  good- 
sized  billet  of  hard  wood  and  count  the  rings  of  annual 
growth.  How  old  was  the  tree  or  the  bough  from  which 
it  was  taken  ?  Was  its  growth  uniform  from  year  to  year  ? 
How  do  you  know  ?  Are  the  rings  broadest,  as  a  general 
thing,  toward  the  center  or  the  circumference?  How  do 


WOOD    STRUCTURE  167 

you  account  for  this  ?  Is  each  separate  ring  of  uniform 
thickness  all  the  way  round?  Mention  some  of  the  cir- 
cumstances that  might  cause  a  tree  to  grow  less  on  one 
side  than  on  the  other ;  such,  for  instance,  as  too  great 
shading,  lack  of  foliage  development  from  one  cause  or 
another,  exposure  of  roots  by  denudation,  etc.  Are  the 
rings  of  the  same  thickness  in  all  kinds  of  wood  ?  Which 
are  the  most  rapid  growers,  those  with  broad  or  with  nar- 
row rings  ?  Do  you  notice  any  difference  in  the  texture 
of  the  wood  in  rapid  and  in  slow  growing  trees  ?  Which 
makes  the  better  timber  as  a  general  thing,  and  why  ? 


310.  — Vertical  section  through  a  black  oak  (from  PINCHOT,  U.S.  Dept.  of  Agr.). 


236.  Heartwood  and  Sapwood.  —  Notice  that  in  some 
of  your  older  specimens  (cedar,  black  walnut,  barberry, 
black  locust,  chestnut,  oak,  Osage  orange,  show  the  differ- 
ence distinctly)  the  central  part  is  different  in  color  and 
texture  from  the  rest.  This  is  because  the  sap  gradually 
abandons  the  center  (Sec.  224)  to  feed  the  outer  layers 
where  growth  in  dicotyls  takes  place ;  hence,  the  outer  part 
of  the  stem  usually  consists  of  sapwood,  which  is  soft  and 
worthless  as  timber,  while  the  dead  interior  forms  the 


i68 


THE   STEM    PROPER 


durable  heartwood  so  prized  by  lumbermen.  The  heart- 
wood  is  useful  to  the  plant  principally  in  giving  strength 
and  firmness  to  the  axis.  It  will  now  be  seen  why  gird- 
ling a  stem,  that  is,  chipping  off  a  ring  of  the  softer  parts 

all  round,  will  kill  it,  while 
we  often  see  vigorous  and 
healthy  trees  with  the  cen- 
ter of  the  trunk  entirely 
hollow. 


237.  Vertical  Arrange- 
ment. —  In  studying  the 
vertical  arrangement  of 
stems  two  sections  are  nec- 
essary, a  radial  and  a  tan- 


311-313.  —  Diagrams    of    sections    of 
timber:    311,  cross  section;  312,  radial; 


313,  tangential   (from  FiNCHOT,  u.s.    gentia!   one.      The   former 

Dept.  ofAgr.). 

^passes  along  the  axis,  split- 
ting the  stem  into  halves  (Fig.  312);  the  latter  cuts 
between  the  axis  and  the  perimeter,  splitting  off  a  segment 
from  one  side  (Fig.  313). 

238.  The  Graining  of  Timber.  —  It  is  the  medullary  rays 
that  constitute  the  characteristic  graining  of  different 
woods.  In  a  chip  of  red  oak  or  chestnut  from  just  beneath 


3*4-  —  Tangential  section  of  mountain  ash,  showing  ends  of  the  medullary  rays. 

the  bark  their  cut  ends  can  be  seen  very  distinctly  with  the 
naked  eye.  Split  a  thicker  chip  of  the  same  kind  parallel 
with  the  medullary  rays  and  notice  the  difference,  the 
rays  now  appearing  as  silvery  bands  traversing  the  wood. 


WOOD   STRUCTURE  169 

Compare  the  graining  of  your  specimens,  or  of  the  floor- 
ing, window  casings,  doors,  desks,  benches,  etc.,  of  your 
schoolroom  with  Figures  312  and  313,  and  tell  what  kind 


315.  —  Sections  of  sycamore  wood  (from  PlNCHOT,  U.S.  Dept  of  Agr.)  : 
a,  tangential ;  b,  radial ;  c,  cross. 

of  cut  was  made  in  each  case  and  show  how  the  appearance 
of  the  timber  has  been  affected  by  it. 

239.  Knots.  —  Look  for  a  billet  with  a  knot  in  it.  Notice 
how  the  rings  of  growth  are  disturbed  and  displaced  in  its 
neighborhood.  If  the  knot  is  a  large  one,  it  will  itself 


316.  —  Sections  of  white  pine  wood  (from  PlNCHOT,  U.S.  Dept.  of  Agr.). 

have  rings  of  growth.  Count  them,  and  tell  what  its  age 
was  when  it  ceased  to  grow.  Notice  where  it  originates. 
Count  the  rings  from  its  point  of  origin  to  the  center  of 
the  stem.  How  old  was  the  tree  when  the  knot  began  to 
form  ?  Count  the  rings  from  the  origin  of  the  knot  to  the 


THE   STEM   PROPER 


circumference  of  the  stem ;  how  many  years  has  the  tree 
lived  since  the  knot  was  formed  ?  Does  this  agree  with 
the  age  of  the  knot  as  deduced  from 
its  own  rings  ?  (As  the  tree  may  con- 
tinue to  live  and  grow  indefinitely  after 
the  bough  which  formed  the  knot  died 
or  was  cut  away,  there  will  probably 
be  no  correspondence  between  the  two 
sets  of  rings,  especially  in  the  case  of 
old  knots  that  have  been  covered  up 
and  embedded 
in  the  wood.) 


317.  —  Section    of   tree 
trunk  showing  knot. 


: 


The  longer  a  dead  branch  remains 
on  a  tree  the  more  rings  of  growth 
will  form  around  it  before  covering 
it  up,  and  the  greater  will  be  the 
disturbance  caused  by  it.  Hence, 
timber  trees  should  be  pruned  while 
very  young,  and  the  parts  removed 
should  be  cut  as  close  as  possible  to 
the  main  branch  or  trunk.  Some- 
times knots  injure  lumber  very 
much  by  falling  out  and  leaving  the 
holes  that  are  so  often  seen  in  pine 
boards.  In  other  cases,  however, 
when  the  knots  are  very  small,  the  grown  in  the  open;  319,  from 

.  .  .  .   ,         ,  tree  grown  in  a  dense  forest. 

irregular  markings  caused  by  them 

add  greatly  to  the  beauty  of  the  wood.  The  peculiar 
marking  of  bird's-eye  maple  is  caused  by  abortive  buds 
buried  in  the  wood. 


- 


318  319 

318,  319. —  Diagrams  of  tree 
trunks,  showing  knots  of  dif- 
ferent ages:  318,  from  tree 


PRACTICAL  QUESTIONS 

1.  Name  the  principal  timber  trees  of  your  neighborhood.     What 
gives  to  each  its  special  value? 

2.  Which  is  better  for  timber,  a  tree  grown  in  the  open,  or  one  in 
a  forest,  and  why?     (239.) 

3.  What  are  the  objects  to  be  attained  in  pruning  timber  trees? 
Orchard  and  ornamental  trees? 


WOOD    STRUCTURE 


I/I 


320.  —  Timber  tree  spoiled  by  standing  too  much  alone  in  early  yo^ith  (from 
PlNCHOT,  U.  S.  Dept.  of  Agr.) .  Notice  how  the  crowded  young  timber  in  the 
background  is  righting  itself,  the  lower  branches  dying  off  early  from  overshading, 
leaving  tall,  straight,  clean  boles. 


I72  THE    STEM   PROPER 

4.  What  is  the  difference  between  timber  and  lumber?     Between  a 
plank  and  a  board?     Between  a  log,  stick,  block,  and  billet? 

5.  Is  the  outer  bark  of  any  use  to  a  tree,  and  if  so,  what?     (176, 
219.) 

6.  Why  does  sapwood  decay  more  quickly  than  heartwood? 

FIELD  WORK 

Make  a  study  of  the  various  climbing  plants  of  your  neighborhood 
with  reference  to  their  modes  of  ascent,  and  the  effect,  injurious,  or  other, 
upon  the  plants  they  cling  to.  Note  the  direction  of  twining  stems  and 
tendrils,  and  their  various  adaptations  to  their  office.  Consider  whether 
the  twining  habit  might  not  lead  to  parasitism,  especially  in  the  case 
of  soft-stemmed  twiners  when  brought  into  contact  with  soft-stemmed 
annuals.  Observe  the  various  habits  of  stem  growth ;  prostrate,  de- 
clined, ascending,  etc.,  and  see  what  adaptation  to  circumstances  can 
be  detected  in  each  case. 

Notice  the  shape  of  the  different  stems  met  with,  and  learn  to 
recognize  the  forms  peculiar  to  certain  of  the  great  families.  Observe 
the  various  appliances  for  defense  and  protection  with  which  they  are 
provided,  and  try  to  find  out  the  meaning  of  the  numerous  grooves, 
ridges,  hairs,  prickles,  and  secretions  that  are  found  on  stems.  Always 
be  on  the  alert  for  transformations,  and  learn  to  recognize  a  stem  under 
any  disguise,  whether  thorn,  tendril,  foliage,  water  holder,  etc. 

Note  the  color  and  texture  of  the  bark  of  the  different  trees  you  see, 
and  learn  to  distinguish  the  most  important  by  it.  Observe  the  differ- 
ence in  texture  and  appearance  of  the  bark  on  old  and  young  boughs 
of  the  same  species.  Try  to  account  for  the  varying  thickness  of  the 
bark  on  different  trees  and  on  different  parts  of  the  same  tree.  Farmers 
are  generally  engaged  in  clearing  and  pruning  at  this  season,  and  it  will 
probably  not  be  difficult  to  get  all  the  specimens  needed  among  the 
rubbish  they  are  clearing  away.  Notice  the  difference  in  the  timber 
of  the  same  species  when  grown  in  different  soils,  at  different  ages  of 
the  tree,  and  in  healthy  and  weakly  specimens. 


VII.     BUDS   AND    BRANCHES 


BRANCHING   STEMS 

MATERIAL.  —  Twigs  of  hickory  and  buckeye,  or  other  alternate  and 
opposite  leaved  plants  with  well-developed  terminal  buds.  A  larger 
bough  of  each  should  also  be  provided,  and  where  practicable,  twigs  of 
several  different  kinds  for  comparison.  Lilac,  horse-chestnut,  maple, 
ash,  viburnum,  are  good  examples  of  opposite  buds. 

240.  Modes  of  Branching.  —  Compare  the  arrangement 
of  the  boughs  on  a  pine,  cedar,  magnolia,  etc.,  with  those 
of  the  elm,  maple,  apple,  or  any  of  our  common  deciduous 

trees.     Draw  a  diagram  of  each  showing 

the   two   modes   of  growth.      The   first 

represents  the  excurrent  kind,  from  the 

Latin   excurrere,    to 

run  out;  the  second, 

in  which  the  trunk 

seems  to  divide    at 

a  certain  point  and 

flow  away  and  lose 

itse  If      in      the 

branches,   is   called 

deliquescent,      from 

the     Latin    dclique- 

scere,  to  melt  or  flow 

away.      The    great 
majority  of  stems,  as  a  little  observation  will  show,  present 
a  mixture  of  the  two  modes. 

241.  Terminal  and  Axillary  Buds.  —  Notice  the  large 
bud  at  the  end  of  a  twig  of  hickory,  sweet  gum,  beech, 
cotton  wood,  etc.     This  is  called  the  terminal  bud  because 


321. —  Diagram   of 
current  growth. 


174 


BUDS   AND   BRANCHES 


it  terminates  its  branch.  Notice  the  leaf  scars  on  your 
twig,  and  look  for  the  small  buds  just  above  them. 
These  are  lateral,  or  axillary  buds,  so 
called  because  they  spring  from  the  axils 
of  the  leaves.  How  many  leaves  did  your 
twig  bear?  How  many  ranked?  What 
difference  in  size  do  you  notice  between 
the  terminal  and  lateral  buds? 


242.  The  Leaf  Scars.  —  Examine  the  leaf 
scars  with  a  hand  lens,  and  observe  the 
number  and  position  of  the  little  dots  in 
them.  (Ailanthus,  varnish  tree,  and  china 
323.-Youngbud  tree  show  these  very  distinctly.)  Refer  to 
Section  219,  and  say  what  these  dots  are. 


of     hickory      (after 
GRAY)  :  t,  terminal 

scl^  left'  bygbu°d 


243.   Bud   Scales   and    Scars.  —  Notice 
scales  of  previous    th       t     t    hard  scaies   by  which    all   the 

year;  s,  leaf  scars; 
/,/,  lenticels;  tr,  leaf 
traces. 


buds  are  covered.  Pull  these  away  from 
the  terminal  one  and  notice  the  ring  of 
scars  that  they  leave  around  the  base  of  the  bud.  Look 
lower  down  on  your  twig  for  a  ring  of  similar  scars  left 
from  last  year's  bud.  Is  there  any  difference  in  the 
appearance  of  the  bark  above  and  below  this  ring  ?  If  so, 
what  is  it,  and  how  do  you  account  for  it  ?  Is  there  more 
than  one  of  these  rings  of  scars  on  your  twig,  and  if  so, 
how  many  ?  How  old  is  the  twig  and  how  much  did  it 
grow  each  year  ?  Has  its  growth  been  uniform  or  did 
it  grow  more  in  some  years  than  others  ? 

244.  Different  Rates  of  Growth.  —  Notice  the  very  great 
difference  between  branches  in  this  respect.  Sometimes 
the  main  axis  of  a  shoot  will  have  lengthened  from  twenty 
to  fifty  centimeters  (eight  to  twenty  inches)  or  more  in  a 
single  season,  while  some  of  the  lateral  ones  will  have 
grown  but  an  inch  or  two  in  four  or  five  seasons.  One 
reason  of  this  is  because  the  terminal  bud,  being  on  one  of 
the  great  trunk  lines  of  sap  movement,  gets  a  larger  share 
of  nourishment  than  the  rest,  and  being  stronger  and  better 


BRANCHING   STEMS 


175 


developed,  starts  out  in  life  with  superior  advantages  of 
position.  Then,  too,  in  ordinary  upright  stems  the  sap 
flow  is  strongest  in  the  upper  part  of  the  stem,  as  may 
be  shown  by  selecting  two  healthy  seedlings  as  nearly  as 
may  be  of  the  same  size  and  height,  inverting  one  of  them 
as  described  in  Section  159,  and  keeping  it  in  this  position 
for  several  days  by  tying  or  by  attaching  a  weight  to  it, 
while  leaving  the  other  upright.  Watch  their  growth  for 
a  week  or  ten  days  and  note  results. 

Make  a  drawing  of  your  specimen,  showing  all  the 
points  brought  out  in  the  examination  just  made.  Cut 
sections  above  and  below  a  set  of  bud  scars  and  count 
the  rings  of  annual  growth  in  each  section.  What  is  the 
age  of  each  ?  How  does  this  agree  with  your  calculation 
from  the  number  of  scar  rings  ? 

245.  Irregularities. — Take  a  larger  bough  of  the  same 
kind  that  you  have  been  studying,  and  observe  whether 
the   arrangement   of    branches 

on  it  corresponds  with  the 
arrangement  of  buds  on  the 
twig.  Did  all  the  buds  develop 
into  branches  ?  Do  those  that 
did  develop  all  correspond  in 
size  and  vigor  ?  If  all  the  buds 
developed,  how  many  branches 
would  a  tree  produce  every 
year  ? 

In  the  elm,  linden,  beech, 
hornbeam,  hazelnut,  willow, 
and  various  other  plants,  the 

....  ..  .         324.— Bud  development  of  beech: 

terminal  bud  always  dies  and  a.  as  it  is>  many  buds  failing  to  de_ 
the  one  next  in  order  takes  its  vel°P'  *•  as  h  would  be  if  a11  the 

.  .    .  .  buds  were  to  live. 

place,  giving  rise  to  the  more 

or  less  zigzag  axis  that  generally  characterizes  trees  of 

these  species. 

246.  Forked  Stems.  —  Take  a  twig  of  buckeye,  horse- 
chestnut,  or  lilac,  and  make  a  careful  sketch  of  it,  show- 


1 76 


BUDS   AND   BRANCHES 


ing  all  the  points  that  were  brought  out  in  the  examination 
of  your  previous  specimen.  Which  is  the  larger,  the  lateral 
or  the  terminal  bud  ?  (If  lilac  is  used,  there 
will  probably  be  no  terminal  bud.)  Is  their 
arrangement  alternate  or  opposite?  What 
was  the  leaf  arrangement  ?  Count  the  dots 
in  the  leaf  scars ;  are  they  the  same  in  all  ? 
If  all  the  buds  had  developed  into  branches, 
how  many  would  spring  from  a  node  ? 
Look  for  the  rings  of  scars  left  by  the  last 
season's  bud  scales.  Do  you  find  any  twig 
_o  osite.  of  more  than  one  year's  growth,  as  measured 
leaved  twig  of  by  the  scar  rings  ? 

Look  down  between  the  forks  of  a 
branched  stem  for  a  round  scar.  This  is  not  a  leaf  scar, 
as  we  can  see  by  its  shape,  but  one  left  by  the  last  season's 
flower  cluster.  The  flower,  as  we  all  know,  dies  after 
perfecting  its  fruit,  and  so  a  flower  bud  can  not  continue 
the  growth  of  its  axis,  as  other  buds  do,  but  has  just  the 
opposite  effect  and  stops  all  further  growth  in  that  direc- 
tion. Hence,  stems  and  branches  that  end  in  a  flower 
bud  can  never  develop  either  excurrent 
or  ordinary  deliquescent  growth,  but 
are  characterized  by  short  branches 
and  frequent  forking.  The  same  thing 
happens  when,  for  any  reason,  the 
terminal  bud  is  destroyed  or  injured 
either  artificially,  or  through  natural 
processes,  as  in  the  lilac,  where  it 
is  frequently  aborted  and  its  place 
usurped  by  the  two  nearest  lateral 
ones,  which  put  forth  on  each  side  of  326. -Diagrams of dichot- 

omous  branching. 

it  and  continue  the  growth  of  the 
branch  in  two  forks  instead  of  a  single  axis.  This  gives 
rise  to  the  kind  of  branching  which  we  see  exemplified  in 
the  lilac,  buckeye,  horse-chestnut,  dogwood,  jimson  weed, 
etc.,  designated  by  botanists  as  dichotomons,  or  two-forked. 
Draw  a  diagram  of  the  buckeye,  or  other  dichotomous 


BRANCHING    STEMS 


177 


stem  as  it  would  be  if  all  the  buds  developed  into  branches, 
and  compare  it  with  your  diagrams  of  excurrent  and  deli- 
quescent growth. 

247.  Definite  and  Indefinite  Annual  Growth.  —  The  pres- 
ence or  absence  of  terminal  buds  gives  rise  to  another  im- 
portant distinction  in  plant  development  —  that  of  definite 
and  indefinite  annual  growth.     Compare  with  any  of  the 
twigs  just  examined,  a  branch  of  rose,  honey  locust,  sumac, 
mulberry,  etc.,  and  note  the  difference  in  their  modes  of 
termination.     The  first  kind,  where  the  bough  completes 
its  season's  increase  in  a  definite  time  and  then  devotes 
its  energies  to  developing  a  strong  terminal  bud  to  begin 
the  next  year's  work  with,  are  said  to  make  a  definite  or 
determinate  annual  growth.     Those  plants,   on  the  other 
hand,  which   make  no   provision   for   the  future   but  go 
straight  on  flourishing  and  rejoicing,  like  the  grasshopper 
in  the  fable,  till  the  cold  comes  and  literally  nips  them  in 
the  bud,  are  indefinite,  or  indeterminate  annual  growers. 
Notice  the  effect  of  this  habit  upon  their  mode  of  branch- 
ing.    The  buds  toward  the  end  of  each  shoot,  being  the 
youngest  and  tenderest,  are   most   readily  killed   off   by 
frost  or  other  accident,  and  hence  the 

new  branches  spring  mostly  from  the 
older  and  stronger  buds  near  the  base 
of  the  stem.  It  is  this  mode  of  branch- 
ing that  gives  to  plants  of  this  class 
their  peculiar  bushy  aspect.  Such 
shrubs  generally  make  good  hedges  on 
account  of  their  thick  undergrowth. 
The  same  effect  can  be  produced  arti- 
ficially by  pruning. 

248.  Differences  in  the  Branching  of 
Trees.  —  We  are  now  prepared  to  un- 
derstand something  about   the   causes 
of  that  endless  variety  in  the  spread  of 

bough  and  sweep  of  woody  spray  that      327-— Winter  spray  of 

...  .  ash,  an    opposite-leaved 

makes  the  winter  woods  so  beautiful,    tree. 

ANDREWS'S  EOT. —  12 


!7g  BUDS   AND    BRANCHES 

Where  the  terminal  bud  is  undisputed  monarch  of  the 
bough,  as  in  the  pine  and  fir,  or  where  it  is  so  strong 
and  vigorous  as  to  overpower  its  weaker  brethren  and 
keep  the  lead,  as  in  the  magnolia 
and  holly,  we  have  excurrent 
growth.  In  plants  like  the  oak 
and  apple,  on  the  other  hand, 
where  all  the  buds  have  a  more 
nearly  equal  chance,  the  lateral 
branches  show  more  vigor  and  the 
result  is  either  deliquescent  growth, 
or  a  mixture  of  the  two  kinds.  In 
the  elm  and  beech,  where  the  usurp- 
ing pseudo-terminal  bud  keeps  the 

328.  —  Winter  spray  of  elm.  ,  ,  1        •, 

mastery,  but  does  not  completely 

overpower  its  weaker  brethren,  we  find  the  long,  sweeping, 
delicate  spray  characteristic  of  those  species.  Examine 
a  sprig  of  elm  and  notice  further  that  the  flower  buds  are 
all  down  near  the  base  of  the  stem,  while  the  leaf  buds 
are  near  the  tip.  The  chief  development  of  the  season's 
growth  is  thus  thrown  toward  the  end  of  the  branch,  giving 
rise  to  that  fine,  feathery  spray  which  makes  the  elm  an 
even  more  beautiful  object  in  winter  than  in  summer. 

An  examination  of  the  twigs  of  other  trees  will  bring 
out  the  various  peculiarities  that  affect  their  mode  of 
branching.  The  angle,  for  instance,  which  a  twig  makes 
with  its  bough  has  a  great  effect  in  shaping  the  contour 
of  the  tree.  As  a  general  thing,  acute  angles  produce 
slender,  flowing  effects  ;  right,  or  obtuse  angles,  more  bold 
and  rugged  outlines. 

PRACTICAL  QUESTIONS 

1 .  Has  the  arrangement  of  leaves  on  a  twig  anything  to  do  with  the 
way  a  tree  is  branched?     (68,  241 .) 

2.  Why  do  most  large  trees  tend  to  assume  the  excurrent,  or  axial 
mode  of  growth  if  let  alone?     (244.) 

3.  If  you  wished  to  alter  the  mode  of  growth,  or  to  produce  what 
nurserymen  call  a  low-headed  tree,  how  would  you  prune  it?    (246,  247.) 

4.  Would  you  top  a  timber  tree?     (246,  247.) 


BUDS  179 

5.  Are  low-headed  or  tall  trees  best  for  an  orchard? 

6.  Why  is  the  growth  of  annuals  generally  indefinite? 

7.  Name  some  trees  of  your  neighborhood  that  are  conspicuous  for 
their  graceful  winter  spray. 

8.  Name  some  that  are  characterized  by  the  sharpness  and  boldness 
of  their  outlines. 

9.  Account  for  the  peculiarities  in  each. 

BUDS 

MATERIAL.  —  Expanding  buds  of  any  of  the  kinds  used  in  Sections 
240-248  and  of  tulip  tree,  magnolia,  or  other  plant  with  stipular  leaf 
scales.  The  buds  should  be  in  different  stages  of  development,  some 
of  them  partly  expanded.  Beech,  elm,  oak,  sycamore,  hackberry,  fig, 
will  any  of  them  serve  as  examples  of  stipular  scales,  but  it  is  advisable 
always  to  use  the  largest  buds  obtainable.  City  schools  might  get  a 
young  India  rubber  tree  from  a  nursery,  or  buds  of  cultivated  magnolia 
from  a  florist.  Gummy  buds  like  horse-chestnut  and  Lombardy  poplar 
should  be  soaked  in  warm  water  before  dissecting,  to  soften  the  gum. 
Buds  with  heavy  fur  on  the  scales,  or  on  the  parts  within  them,  can  not 
very  well  be  studied  in  section,  but  the  parts  must  be  taken  out  and 
examined  separately.  Where  material  is  scarce,  the  twigs  used  in  Sec- 
tions 240-248  can  be  placed  in  water  and  kept  until  the  buds  begin  to 
expand. 

249.  Study  of  an  Opposite-Leaved  Bud.  —  Examine  a 
twig  of  buckeye,  horse-chestnut,  lilac,  or  maple,  etc.,  just 
as  the  buds  are  beginning  to  unfold.  Make  an  enlarged 
sketch  of  the  terminal  one  (in  the  lilac,  usually  two), 
showing  the  relative  size  and  position  of 
the  scales. 


H-H- 


ntt 


250.  Arrangement  of  the  Scales. — 
Notice  the  manner  in  which  the  scales 
overlap,  so  as  to  break  joints,  like 
shingles  on  the  roof  of  a  house.  Leaves 
or  scales  that  overlap  in  this  way  are  329. -Diagram  of  op- 
said  to  be  imbricated.  Where  the  posi 
leaves  are  opposite,  as  in  the  specimen  we  are  examining, 
the  manner  of  imbrication  is  very  simple.  Remove  the 
scales  one  by  one,  representing  the  number  and  position 
of  the  pairs  by  a  diagram  after  the  model  given  in  Figure 
329.  (If  the  scales  are  too  brittle  to  be  removed  without 


!8o  BUDS   AND   BRANCHES 

breaking,  use  a  bud  that  has  been  soaked  in  warm  water  for 
an  hour  or  two.)  How  many  pairs  of  scales  .are  there  in 
each  set  ?  How  does  their  arrangement  correspond  with 
that  of  the  leaf  scars  upon  the  stem  ?  What  difference  in 
size  and  texture  do  you  observe  between 
the  outer  and  inner  scales  ? 

251.  Nature  of  the  Scales.  —  Hold  up 
to  the  light  one  of  the  scales  from  a 
partly  expanded  bud  and  see  whether 
it  is  veined,  and  in  what  way.  Does 
this  correspond  with  the  venation  of 
foliage  leaves?  Can  you  make  out 
what  the  scales  represent  ?  Their 
arrangement  is  the  same  as  that  of  the 
leaves,  so  they  must  represent  the  leaf 
or  some  part  of  it,  as  the  petiole  or  the 
stipules.  In  the  lilac  and  various  other 
buds  they  are  found  in  all  stages  of 
transition  from  scales  to  true  leaves, 
from  which  their  real  nature  may  readily 
be  inferred.  In  the  common  buckeye 
and  the  horse-chestnut  the  transition  is 
r  not  so  apparent,  but  a  comparison  with 

330.—  Development  of 

.the  parts  of  the  bud  in  the    Figure    3  30   will   show   that   they   are 

buckeye  Rafter  GRAY).        altered    petioles 

252.  Use  of  the  Scales. — What  purpose  do  the  scales 
serve  ?     You   can   best   answer   this    question   by  asking 
yourself  what  is  the  use  of  the  shingles  on  the  roof  of  a 
house,  or  of  the  cloaks  with  which  we  wrap  ourselves  in 
winter  ?     Notice  how  thick  and  hard  the  outer  ones  are, 
and  how  the  inner  ones  envelop  the  tender  parts  within 
like  blankets.     As  we  sometimes  coat  our  roofs  with  tar  and 
cement,  so  these  scales,  especially  in  cold  climates,  are  often 
coated  with  gum  for  greater  security  against  the  weather. 

253.  Internal  Structure  of  the  Bud.  -    Make  a  cross  sec- 
tion of  a  bud  and  sketch  it  as  it  appears  under  the  lens. 


BUDS 


Next  draw  a  vertical  section,  then  remove  the  contents  and 
see  what  they  are.  There  will  be  no  difficulty  in  recogniz- 
ing the  circle  of  young  leaves  just  within 
the  scales.  How  many  of  these  rudi- 
mentary leaves  are  there  ?  Is  their 
arrangement  alternate  or  opposite  ?  No- 
tice the  down  with  which  they  are  covered 
(in  the  horse-chestnut  and  buckeye). 
Have  the  mature  leaves  of  these  plants 
any  covering  of  th'is  sort?  What  is  its 
use  here  ? 

254.  Folding  of  the  Leaves.  —  Notice 
the  manner  in  which  the  young  leaves  are 
folded    in   the   bud.      This  is   called   by 
botanists  vernation,  or  prefoliation,  words 
meaning  respectively  "  spring  condition  " 

and     "  condition     preceding    the     leaf."  332 

Leaves  have  to  be  packed  in  the  bud  so       331-332-— Buds  of 

.         ,  ...          maple:    331,  vertical 

as   to   occupy   the   least   space   possible,    section  of  a  twig ;  332> 
and  in  different  plants  they  will  be  found    cross  section  throilsh 

*  an  end  bud,  showing 

folded  in  a  great  many  different  ways,  as    folded  leaves  in  cen- 
is  best  suited  to  the  shape  and  texture    ter  and  s'ales  sur' 

rounding  them. 

of  the  leaf  and  the  space  available  for  it 
in  the  bud.     When  doubled  back  and  forth  like  a  fan,  or 
crumpled  and  folded  as  in  the  buckeye,  horse-chestnut, 
and  maple,  the  vernation  is  plicate  (Fig.  332). 

255.  Position  of  the  Flower  Cluster.  —  What  do  you  find 
within  the  circle  of  leaves  ?     Examine  one  of  the  smaller 
axillary  buds,  and  see  if  you  find  the  same  object  within  it. 
If  you  are  in  any  doubt  as  to  what  this  object  is,  examine 
a  bud  that  is  more  expanded  and  you  will  have  no  difficulty 
in  recognizing  it  as  a  rudimentary  flower  cluster.     Notice 
its  position  with  reference  to  the  scales  and  leaves.     Being 
at  the  center  of  the  bud,  it  will,  of  course,  terminate  its 
axis  when  the  bud  expands,  and  the  growth  of  the  branch 
will  culminate  in  the  flower.     The  branching  of  the  buck- 
eye  (or   horse-chestnut)   must,   then,  be  of    what   order  ? 


1 82 


BUDS   AND   BRANCHES 


Compare  your  drawings  with  the  section  of  a  hyacinth 
bulb  or  jonquil,  and  note  the  similarity  in  position  of  the 
flower  clusters. 

256.  Study  of  an  Alternate- 
Leaved  Bud.  —  Examine  a  large 
terminal  bud  of  hickory,  just 
about  to  open.  (Apple,  pear, 
cherry,  etc.,  may  be  substituted 
if  necessary.)  How  do  the 
scales  differ  in  shape  and  tex- 
ture from  those  already  exam- 
ined ?  Pick  off  the  scales  one 

333. -Cross  section   of   a    leaf  j^y    On6j     noting     their     position 

bud  of  the  rose,  showing,  the  alter-  J 

nate  arrangement  of  scales  and  Carefully  and  illustrating  it  by 
rudimentary  leaves:  A  growing  diagram,  as  shown  in  Fig- 
point;  Z.1,  youngest  leaf ;  Z.2,  three  .  ° 

folded  lobes  of  second  leaf;  .s*2,    ure  333.    This  is  another  variety 

scales68  °f  SeC°nd  kaf:  Sel~Se*'    of  the  imbricated  arrangement, 

and  is  by  far  the  most  common, 

though  much  less  simple  than  that  of  opposite-leaved  buds. 
How  does  it  correspond  with  the  arrange- 
ment of  leaf  scars  on  the  stem  ?  Refer 
to  Section  52,  and  say  to  what  order  of 
phyllotaxy  it  belongs.  Notice  the  grad- 
ual change  in  the  size  and  appearance 
of  the  scales  from  the  outside  toward 
the  center.  Can  you  give  any  reasons 
for  regarding  them  as  transformed 
leaves  ?  Sketch  the  bud  in  cross  and 
vertical  section  (unless  this  is  impracti- 
cable on  account  of  the  fur)  and  then 
remove  the  contents.  Notice  the  copi- 
ous fur  on  the  inner  scales  ;  of  what  use 
is  it?  Examine  with  a  lens  the  little  Jj°"lir°ry  ^^^3  • 
furry  bodies  within  the  scales  and  see  pouter  scales;  /.folded 
if  you  can  tell  what  they  are  ;  if  you  can  leaf ;  r>  recePtacle- 
not,  get  a  bud  that  is  partly  unfolded  and  you  will  probably 
have  no  trouble  in  recognizing  them  as  rudimentary  leaves. 


334.— Vertical  see- 


BUDS 


183 


Notice  the  manner  in  which  the  separate  leaflets  are  folded 
in  the  bud  and  make  a  diagram  of  it ;  how  does  it  differ 
from  that  of  the  buckeye  ?  (Vernation 
is  always  best  observed  in  partly  ex- 
panded buds.)  This  kind  of  vernation, 
in  which  each  leaf  or  leaflet  is  rolled 
over  from  one  side  to  the  other,  is  called 
convolute.  Plum,  apple,  canna,  calla 
lily,  offer  good  examples  of  it. 

Are  there  any  flower  clusters  in  your 
hickory  bud  ?  if  not,  look  for  one  that 
has  them.  Are  they  axillary  or  ter- 
minal? Will  they  stop  the  further 
development  of  their  branch  ?  Why 
or  why  not  ? 


335.  —  Expanding  bud 
of  English  walnut,  show- 
ing twice  conduplicate 
vernation. 


257.    Buds  with  Stipular  Scales.  —  Sketch  a  bud  of  the 
tulip  tree,  or  other  magnolia,  on  the  outside.     (The  India 
rubber    tree,    oak,    beech,    and    hack- 
berry,  furnish  other  examples  of  stip- 
ular   scales.)      How   does   it   differ   in 
appearance  from  the  ones  already  ex- 
s    amined  ?      Remove   the   outer   pair    of 
scales   and   observe  that  (in  the  tulip 
.5    tree)  their   edges    do    not   overlap    as 
in    the    imbricated    arrangement,    but 
merely  touch,    or   in 
botanical     language, 

336.-Bud  of  tulip    are  valvate.     Notice 
tree,   showing   stipuiar    the  difference  in  color 

scales:,.  ..stipules.  between       the       outer 

and  inner  scales.     Why  are  the  outer 
pair  so  hard  and  thick  ?     Draw  a  cross 
section  of  the  bud  as  it  appears  under 
the  lens,  showing  the  small  round  objects    cessive    leaves    (1-7) 
that  appear  here  and  there  between  the    v 
scales.     Can  you  make  out  what  they  are  ?     Draw  2  verti- 
cal section.     Do  you  see  anything  like  a  flower  bud  ?     If 


1 84 


BUDS   AND   BRANCHES 


so,  is  it  a  cluster  or  a  single  flower  ?  (Terminal  buds  in 
the  tulip  tree  are  usually,  but  not  always,  flower  buds.) 
Remove  the  next  pair  of  scales  and  notice  the  rudimentary 
leaf  between  them.  This  outer  leaf  is  often  found  to  be 
dead ;  can  you  account  for  the  fact  ?  Pick  off  the  succes- 
sive pairs  of  scales,  noticing  the  leaf  between  them. 
Observe  that  the  footstalk  of  each  originates  between  the 
bases  of  the  scales.  You  will  have  no  difficulty  now  in 
identifying  the  little  round  dots  in  your  cross  section  as  the 
cut  ends  of  the  petioles.  How  many  pairs  of  scales  are 
there  in  the  bud  ?  How  many  leaflets  ?  Study  their 
arrangement  and  compare  it  with  the  diagram  (Fig.  337). 
How  does  this  correspond  with  the  arrangement  of  leaves 
on  the  stem  ?  Do  you  find  any  clusters  of  bud  scale 
scars  as  in  the  other  specimens  examined? 

258.  What  the  Scales  are.  —  The  bud  scales  here  clearly 
can  not  represent  leaves.  Compare  their  position  at  the 
foot  of  the  petiole  with  what  was  said  in  Section  32  regard- 
ing the  stipules,  and 
decide  what  they  are. 
Notice  that  the  two 
hard  outer  ones  have 
no  leaflet  between  them ; 
this  is  because  they  are 
the  stipules  left  by  the 
last  leaf  of  the  preced- 
ing season,  which  per- 

338.  — Elm  bud  with  succession  of  scales:      sjs<-  on  th~  crpm    rhniio-h 
t.  terminal  bud.    The  scales  are  numbered  in      '  tem'  tn°Ugn 

successive  order  as  they  occur  at  the  nodes,      the     Others     Usually    fall 
9  shows  two  stipular  scales  partly  fused  into 
one ;    10,  an  outer  and  an  inner  stipule,  o.  st 
and  /.  st,  with  a  rudimentary  leaf  between;  n, 
12,  and  13,  the  same.     All  are  separated  to 


the 


show  outline. 


away    soon     after 
leaves  develop. 

In  the  elm  each  scale 
represents     a     pair     of 

stipules,  as  will  be  evident  by  observing  that  they  are 
often  notched  or  bifid  at  the  top,  and  that  the  rudiment- 
ary leaves  stand  opposite  their  scales  instead  of  between 
them. 


BUDS 


I85 


259.  Arrangement  of  Scars.  —  Examine  the  leaf  scars 
at  the  nodes  of  a  twig  of  tulip  tree,  fig,  or  magnolia,  and 
notice  the  ring  encircling  the  stem  at  each 
(Fig.  339).  These  are  the  scars  left  by  the 
stipular  scales  of  the  past  season  as  they 
fell  away.  Where  a  pair  of  scales  is  attached 
with  each  separate  leaf,  they  are  carried 
apart  as  the  nodes  lengthen,  and  thus  the 
scars  are  scattered,  a  pair  at  each  node  all 
along  the  stem,  instead  of  being  compacted 
into  bands  at  the  base  of  the  bud.  They 
are  sometimes  very  persistent,  as  in  the 
common  fig,  where  they  may  often  be  traced 

distinctly  on  stems  ten  to  fif-    /._. 

teen  years  old. 

339.  — Stem  of 
tulip  tree:  j,j,  scars 

260.    Vernation.  —  Notice   left    by    stipuiar 
how    the    two   halves   of   the  ^«?:    ^   k 
leaflets   are  doubled  together 
by  their  inner  faces  and  then  bent  over  on 
the  petiole  (Fig.  336).      The  first  is  called 
340.  — A  partly    condiiplicdte.  and  is  common  in  the  redbud, 

expanded  leaf  of 

beech,    showing    rose,  peach,  cherry,  oak,  Japan  quince,  etc. ; 
piicate-condupii-    tne  secon(j  js  the  inflexcd  mode  of  vernation. 

cate  vernation.  J   . 

This  mixed  vernation  is  very  common.  In  the 
elm  and  beech  the  two  halves  of  the  leaf  are  first  plicate 
and  then  conduplicate  to  each  other  (Fig.  340);  in  the 
purple  magnolia  and  chinquapin  they  are  conduplicate- 
plicate. 


344 


MS 


341-345.  —  Diagrams  of  vernation:  341,  conduplicate  (oak);  342,  convolute 
(cherry) ;  343,  revolute  (dock) ;  344,  involute  (balsam  poplar) ;  345,  plicate 
(sycamore) . 


1 86 


BUDS   AND    BRANCHES 


261.  Forms  of  Vernation.  —  The  varieties  of  vernation 
or  prefoliation  should  be  studied  and  diagrammed  as  they 
are  met  with.  In  addition  to  the  varieties  already  men- 
tioned, there  are  the 

Straight:  not  bent  or  folded  in  any  way,  as 
Japan  honeysuckle,  periwinkle,  St.  John's- 
wort,  dogwood,  etc. 

Involute  (Fig.    344):   violet,    arrow   grass 
(Sagittaria),  lotus,  water  lily,  balm  of  Gilead. 
Revolute  (Fig.    343) :    dock,    willow   oak, 
scarlet  morning-glory  (Ipomea 
coccinea),     rosemary,      azalea, 
persimmon. 

Circinnate  (Fig.  346)  :  ferns, 
sundew. 


346.  —  Circinnate 
bud  of  fern. 


262.  Dormant  Buds. — A  bud 
may  often  lie  dormant  for 
months  or  even  years,  and 
then,  through  the  injury  or  destruction  of 
its  stronger  rivals,  or  some  other  favoring 
cause,  develop  into  a  branch.  Such  buds  are 
said  to  be  latent  or  dormant.  The  sprouts 
that  often  put  up  from  the  stumps  of  felled 
trees  originate  from  this  source. 


H 
I 

347. -Twig  of 
red  maple,  show- 
ing supernumer- 
ary bud,  b ;  rs, 
ring  of  scars  left 
by  last  year's 
bud  scales  (after 

GRAY). 


263.  Supernumerary  Buds.  —  Where  more 
than  one  bud  develops  at  a  node,  as  is  so 
often  the  case  in  the  oak,  maple,  honey  locust, 
etc.,  all  except  the  normal  one  in  the  axil  are  supernumerary 
or  accessory.  These  must  not  be  confounded  with  adventi- 
tious buds,  or  those  that  occur  elsewhere  than  at  a  node. 


PRACTICAL  QUESTIONS 

1.  Why  do  annuals  and   herbaceous  plants  generally  have  unpro- 
tected buds?     (252.) 

2.  Why  is  the  gummy  coating  found  on  the  buds  of  the  horse-chest- 
nut and  balm  of  Gilead  wanting  in  their  southern  representatives,  the 
buckeye  and  silver  poplar?     (252.) 


INFLORESCENCE  1 8; 

3.  Can  you  name  any  plants  the  buds  of  which  serve  as  food  for  man  ? 

4.  How  do  flower  buds  differ  in  shape  from  leaf  buds? 

5.  At  what  season  can  the  leaf  bud  and  the  flower  bud  first  be 
distinguished? 

6.  Watch  any  of  the  trees  about  your  home  and  see  when  the  buds 
that  are  to  develop  into  leaves  and  flowers  the  next  year  are  formed. 


INFLORESCENCE 

MATERIAL.  —  A  few  typical  flower  clusters  illustrating  the  definite 
and  indefinite  modes  of  inflorescence.  Some  of  those  mentioned  in 
the  text  are  :  — 

Indefinite  :  hyacinth,  shepherd's  purse,  wall  flower,  parsley,  lilac,  blue 
grass,  smart  weed  (polygonuui),  wheat,  oak,  willow,  clover. 

Definite:  chick  weed,  spurge  (Euphorbia,  various  kinds),  comfrey, 
dead  nettle  (Lainium  aiiiplexicaule),  etc.  Any  other  examples  illus- 
trating the  principal  kinds  of  cluster  will  do  as  well,  but  the  subject 
should  not  be  taught  without  an  examination  of  at  least  a  few  living 
specimens  of  each  sort. 

264.  Definitions.  —  Inflorescence  is  a  term  used  to  denote 
the  position  and  arrangement  of  flowers  on  the  stem.     It 
is  merely  a  mode  of  branch- 
ing   and    follows    the    same 

laws  that  govern  the  branch- 
ing of  ordinary  stems. 

The  stalk  that  bears  a 
flower  is  called  by  botanists 
the  peduncle.  In  a  cluster 
the  main  axis  is  the  com- 
mon peduncle,  or  rhachis,  and 
the  separate  flower  stalks 
pedicels. 

265.  Two  Kinds  of  Inflores- 
cence. —  The      growth      of 
flower  stems,  like  that  of  leaf 
stems,    is    of    two    principal 

348.  —  Solitary  terminal  flower  of  a  lily. 

kinds,  definite  and  indefinite, 

or  as  it  is  frequently  expressed,  determinate  and  indeter- 


188 


BUDS   AND    BRANCHES 


349-  —  Solitary  axillary 
rescence    of    moneywort    (after 
GRAY). 


minate.  The  simplest  kind  of  each  is  the  solitary,  where 
a  single  flower  either  terminates  the  main  axis,  as  the 
daffodil,  trillium,  magnolia,  etc.,  or  springs  singly  from 
the  axils,  as  in  the  running  peri- 
winkle, moneywort,  and  cotton. 

266.  Indeterminate  Inflorescence 
is  always  axillary,  since  the  pro- 
duction of  a  terminal  flower 
would  stop  further  growth  in  that 
direction  and  thus  terminate  the 
development  of  the  axis.  We  have  only  to  imagine  the 
internodes  of  such  a  stem  or  branch  as  that  represented 
in  Figure  349  very  much  shortened,  the  leaves  reduced  to 
bracts  or  wanting  altogether,  and  flowers  or  flower  buds  at 
every  node,  to  have  the 

267.  Raceme,  the  typical  flower  cluster  of  the  indefinite 
sort.  In  such  an  arrangement  the  oldest  flowers  are, 
necessarily,  at  the  lower  nodes,  new 
ones  appearing  only  as  the  axis  length- 
ens and  produces  new  internodes. 
This  will  be  made  clear  by  examining 
a  flowering  stalk  of  hyacinth,  cherry 
laurel  (Primus  caroliniana),  shepherd's 
purse,  or  any  common  weeds  of  the 
mustard  family  that  are  generally  to 
be  found  in  abundance  everywhere. 
It  will  be  seen  that  the  lower  buds 
have  already  fruited  in  the  last  named, 
and  perhaps  the  pods  have  dehisced 
and  shed  their  seed  before  the  upper 
ones  have  even  begun  to  unfold. 
Notice  the  little  scale  or  bract  usually  35°-  —  Raceme  of  milk 
found  at  the  base  of  the  pedicel  in 
flower  clusters  of  this  sort  (in  the  shepherd's  purse  it  is 
wanting).  This  is  a  reduced  leaf,  and  the  fact  that  the 
flower  stalk  springs  from  the  axil,  shows  it  to  be  of 
the  essential  nature  of  a  branch. 


INFLORESCENCE 


189 


Corymb  of  plum 
blossoms. 


268.  The   Corymb. —  Imagine  the  lower   pedicels  of  a 
raceme  to  be  elongated  so  as  to  place  their  flowers  on  a 
level    with    those   of    the   upper   nodes, 

making  a  convex,  or  more  or  less  flat- 
topped  cluster,  as  in  the  wall-flower  and 
hawthorn,  and  we  have  a  modification 
of  the  raceme  called  a  corymb.  In  such 
a  cluster  the  outer  blossoms,  or  those 
on  the  circumference,  proceed  from  the 
lower  axils  and  are,  consequently,  the 
oldest ;  hence,  the  order  of  flowering  351 
is  centripetal,  that  is,  from  the  circum- 
ference to  the  center.  This,  an  inspection  of  Figure  351 
will  show,  is  only  another  way  of  saying  that  it  is  of  the 
indefinite  or  indeterminate  order. 

269.  The  Umbel   is  a   still  further  modification  of  the 
raceme.     The  pedicels  with  their  bracts  are  all  gathered 

at  the  top  of  the  peduncle,  from 
which  they  spread  in  every  direc- 
tion like  the  rays  of  an  umbrella, 
as  the  name  implies.  This,  though 
confined  to  no  one  group,  is  the 
prevalent  type  of  flower  cluster  in 
the  parsley  family,  which  takes  its 
botanical  name,  Umbellifcrce,  from 
its  characteristic  form  of  inflo- 
rescence. The 

352. -Umbel  of  milkweed.         pediCels    of    an   ^ 

umbel  are  generally  called  rays  and  the 
circle  of  bracts  at  the  base  of  the  cluster 
is  an  involucre. 


270.  Compound  Clusters.  —  All  these 
forms  of  inflorescence  may  be  com- 
pound. Most  of  the  parsley  family 
have  compound  umbels.  The  lilac, 
grape,  catalpa,  and  many  grasses  fur- 
nish familiar  examples  of  the  panicle,  353.  — panicieofagrass. 


BUDS   AND   BRANCHES 


which  is  merely  a  compound  raceme,  the  pedicels  of  which 
are  branched  one  or  more  times. 

271.  A  Spike  (Fig.  354)  is  a  raceme  with 
the  flowers  sessile  and  more  or  less  crowded 
together,  as  in  the  plantain,  smartweed, 
wheat,  barley,  etc.  A  form  of  spike  more 
common  in  early  spring  is  the 


272.   Ament,  or  Catkin,   of 

which  we  have  abundant 
examples  in  the  pendent  scaly 
inflorescence  of  the  willow, 
oak,  poplar,  and  most  of  our 
354.— A  spike  common  forest  trees  (Fig. 
355).  A  sessile  corymb  or 


of  the  common 
plantain     (Plan- 


tago  lanceolata).     umbel    gives   rise    to 

273.   The  Head  (Fig.   356),  a  crowded, 
roundish    cluster   like   the   clover,    button-    ca?k?n~ofm<birch 
wood,  sycamore,  etc.      (after  GRAY). 

274.  Diagrams.  —  Do  not  try  to 
learn  all  these  names  by  heart,  but 
look  for  examples  of  the  different 
kinds  of  inflorescence  and  diagram 
them,  using  balls  or  circles  to  sym- 
bolize the  flowers,  as  in  the  models 
given  in  Figures  357  to  361.  The 
order  of  blooming  may  be  shown 
by  using  larger  balls  to  represent 
It  will  be  seen  from  the  diagrams  that 
all  the  forms  of  indefinite  inflorescence  are  derived  from  the 
raceme,  whence  it  is  frequently  spoken  of  as  the  racemose 
type  of  inflorescence. 

275.  Cymose,  or  Definite  Inflorescence.  —  As  the  raceme 
is  the  fundamental  form  of  indefinite  inflorescence,  so  the 
fundamental  form  of  the  definite  or  determinate  kind  is 


Head  of  clover. 


the  older  flowers. 


INFLORESCENCE 


the  cyme,  and  hence,  the  term  "cymose"  is  frequently  used 
as  synonymous  with  determinate  or  definite. 


357  358  359  360  361 

357-361.  —  Diagrams  of  indefinite  inflorescence :  357,  compound  corymb ;  358, 
compound  raceme,  or  panicle;  359,  umbel;  360,  corymb;  361,  raceme. 

276.  Nature  of  the  Cyme.  —  To  understand  the  nature 
of  the  cyme,  study  a  forking  branch  of  common  mouse-ear 
chickweed  (Cerastium  vnlgatum\  corn  cockle,  or  spurge 
{Euphorbia).  Examine  carefully  what  appears  to  be  the 
topmost  cluster  of  blossoms,  and  it  will  be  found  to  consist 
of  a  single  terminal  flower  (probably  already  gone  to 
seed),  with  two  smaller  flower  clusters  rising  from  the 
axils  of  leaves  at  the 
base  of  the  peduncle. 
The  older  blossoms 
in  the  center,  being 
terminal,  stopped  the 
growth  of  the  axis 
in  that  direction  just 
as  we  saw  in  the 
case  of  the  terminal 
flower  bud  of  the 
buckeye,  and  forced 
the  stem  in  continu- 

362.  —  Forking  cyme  of  common  chickweed. 

ing  its  growth  to  send 

out  side  branches  from  the  axils  of  the  topmost  leaves. 
One  or  both  of  these  branchest  will  produce,  or  perhaps 
has  already  produced,  in  turn,  a  terminal  flower  which 
forces  its  branch  to  divide  again,  and  so  on,  forking  indef- 
initely in  a  manner  precisely  analogous  to  the  dichotomous 


1 92 


BUDS    AND    BRANCHES 


forking  of  stems  like  the  buckeye  and  jimson  weed.  By 
looking  down  in  the  next  lower  fork  you  will  probably 
find  the  remains  of  a  still  older  flower  that  terminated 
the  growth  in  that  direction  and  forced  the  stem  to  con- 
tinue its  development  by  sending  off  branches  on  either 
side,  and  so  on,  until  the  remains  of  the  older  flowers  have 
disappeared  and  the  forking  becomes  obscured.  Here  the 
oldest  flower  is  lowest,  not  because,  as  in  the  raceme,  the 
axis  has  continued  to  grow  beyond  it,  but  because  it 
checked  the  further  development  of  its  own  axis  and  has 
been  overtopped  by  new  branches. 

277.    Centrifugal     Inflorescence.  — 

When  the  older  peduncles  are  length- 
ened as  described  in  Section  268,  a 
flat-topped  cyme  is  produced,  which 
is  distinguished  from  the  corymb  by 
its  centrifugal  inflorescence  ;  that  is, 
the  oldest  flower  of  each  cluster  is  in 
the  center,  and  the  order  of  blossom- 
ing proceeds  from  within  toward  the 
circumference,  as  in  the  star-of- 
Bethlehem,  bitterweed  (Helenium 
tenuifolium\  etc.  If  the  cyme  is 
much  compounded,  the  inflorescence 
becomes  very  complicated,  and  as  many  of  the  blossoms 
never  develop,  will  seem  to  have  no  regular  order. 

278.  The  Coiled,  or  Scorpioid  Cyme.  —  A  peculiar  form 
of  cyme  is  found  in  the  coiled  inflorescence  of  the  pink- 
root  (Spigelia\  heliotrope,  comfrey,  etc.      It  occurs  where 
a  cyme  like  that  represented  in  Figure  362  develops  on 
one  side  only.     Its  structure  will  be  made  clear  by  an  in- 
spection of  Figures  365-367. 

279.  Mixed  Inflorescence.  —  We  often  find  the  two  kinds 
of  inflorescence  mixed  in  the  same  cluster.     In  a  panicle 
of  buckeye,  for  example,  the  whole  cluster  is  terminal  with 


363.  —  Flat-topped  cyme  of 
sneezeweed. 


INFLORESCENCE 


193 


reference  to  its  shoot,  while  the  secondary  branches  are 
indefinite,  the  lower  blooming  first.    The  individual  flowers 


364.  —  Scorpioid  cyme. 

of  these  secondary  clusters,  again,  are  of  the  definite  type, 
being  disposed  in  scorpioid  cymes. 


365-367.  —  Diagrams  of  cymose  inflorescence,  with  flowers  numbered  in  the 
order  of  their  development :  365,  cyme  half  developed  (scorpioid)  ;  366,  a  flat- 
topped  or  corymbose  cyme;  367,  development  of  a  typical  cyme. 

280.  Use  of  Terms.  —  The  distinction  between  determi- 
nate and  indeterminate  inflorescence  is  not  strictly  adhered 
to  in  botanical  descriptions,  especially  if  the  clusters  are  at 
all  complicated.  It  is  well  to  remember,  however,  that 

ANDREWS'S  SOT. —  13 


194 


BUDS    AND    BRANCHES 


the  terms  indefinite,  indeterminate,  racemose,  centripetal, 
all  mean  about  the  same  thing ;  namely,  that  the  flowers 
develop  with  the  axis,  or  from  below  upward;  and  the 
terms  definite,  determinate,  cymose,  centrifugal,  are  em- 
ployed to  denote  that  the  order  of  inflorescence  is  contrary 
to  that  of  the  stem  growth,  and  is  constantly  changing  its 
direction. 

281.   Significance  of  the  Clustered  Arrangement.  —  As  a 

general  thing  the  clustered  arrangement  marks  a  higher 
stage  of  development  than  the  solitary,  just  as  in  human 
life  the  rudest  social  state  is  a  distinct  advance  upon  the 
isolated  condition  of  the  savage.  In  plant  life  it  is  the 
beginning  of  a  system  of  cooperation  and  division  of 
labor  among  the  associated  members  of  the  flower  cluster, 
as  will  be  seen  later,  when  we  take  up  the  study  of  the 
flower. 

PRACTICAL  QUESTIONS 

1.  Name  as  many  solitary  flowers  as  you  can  think  of. 

2.  Do  you  find  very  small  flowers,  as  a  rule,  solitary,  or  in  clusters? 

3.  Would  the  separate  flowers  of  the  clover,  parsley,  or  grape,  be 
readily  distinguished  by  the  eye  from  among  a  mass  of  foliage? 

4.  Should  you  judge  from  these  facts  that  it  is,  in  general,  advan- 
tageous to  plants  for  their  flowers  to  be  conspicuous? 

FIELD  WORK 

The  foregoing  lessons  are  themselves  so  full  of  suggestions  for  field 
work  that  it  hardly  seems  necessary  to  add  anything  to  them. 

In  connection  with  Sections  240-248,  the  characteristic  modes  of 
branching  of  the  common  trees  and  shrubs  of  each  neighborhood 
should  be  observed  and  accounted  for.  The  naked  branches  of  the 
winter  woods  afford  exceptional  advantages  for  studies  of  this  kind, 
which  can  not  well.be  carried  on  except  out  of  doors.  Trees  should  be 
selected  for  observation  that  have  not  been  pruned  or  tampered  with  by 
man.  Note  the  effect  of  the  mode  of  branching  upon  the  general  out- 
line of  the  tree ;  compare  the  direction  and  mode  of  growth  of  the 
larger  boughs  with  that  of  small  twigs  in  the  same  species  and  see  51 
there  is  any  general  correspondence  between  them ;  note  the  absence 
of  fine  spray  on  the  boughs  of  large-leaved  trees,  and  account  for  it. 
Account  for  the  flat  sprays  of  trees  like  the  elm,  beech,  hackberry,  etc. ; 


INFLORESCENCE  195 

the  irregular  stumpy  branches  of  the  oak  and  walnut ;  the  stiff,  straight 
twigs  of  the  ash  ;  the  zigzag  switches  of  the  black  locust,  Osage  orange, 
elm,  linden,  etc.  Measure  the  twigs  on  various  species  and  see  if  there 
is  any  relation  between  the  length  and  thickness  of  branches.  Notice 
the  different  trend  of  the  upper,  middle,  and  lower  boughs  in  most 
trees  and  account  for  it.  Observe  the  mode  of  branching  of  as  many 
different  species  as  possible  of  some  of  the  great  botanical  groups  of 
trees  ;  the  oaks,  hickories,  hawthorns,  or  pines,  for  instance,  and  notice 
whether  it  is,  as  a  general  thing,  uniform  among  the  species  of  the  same 
group,  and  how  it  differs  from  that  of  other  groups. 

In  connection  with  Sections  249-263,  buds  of  as  many  different  kinds 
as  possible  should  be  examined  with  reference  to  their  means  of  protec- 
tion, their  vernation  and  phyllotaxy,  and  the  modes  of  growth  result- 
ing from  them.  Compare  the  folding  of  the  cotyledons  in  the  seed 
with  the  vernation  of  the  same  plants,  and  observe  whether  the  folding 
is  the  same  throughout  a  whole  group  of  related  plants,  or  only  for  the 
same  species.  Notice  which  modes  seem  to  be  most  prevalent.  Select 
a  twig  on  some  tree  near  your  home  or  your  schoolhouse  and  keep  a 
record  of  its  daily  growth  from  the  first  sign  of  the  unfolding  of  its 
principal  bud  to  the  full  development  of  all  its  leaves.  Any  study  of 
buds  should  include  an  observation  of  them  in  all  stages  of  develop- 
ment. 

With  Sections  264-281,  study  the  inflorescence  of  the  common  plants 
and  weeds  that  happen  to  be  in  season,  until  you  have  no  difficulty  in 
distinguishing  between  the  definite  and  indefinite  sorts,  and  can  refer 
any  ordinary  cluster  to  its  proper  form.  Notice  whether  there  is  any 
tendency  to  uniformity  in  the  mode  of  inflorescence  among  flowers  of 
the  same  family.  Consider  how  each  kind  is  adapted  to  the  shape  and 
habit  of  the  flowers  composing  it,  and  what  particular  advantage  each 
of  the  specimens  examined  derives  from  the  way  its  flowers  are  clus- 
tered. In  cases  of  mixed  inflorescence  see  if  you  can  discover  any 
reason  for  the  change  from  one  form  to  the  other. 


VIII.    THE  FLOWER 
HYPOGYNOUS   MONOCOTYLEDONS 

MATERIAL. —  Any  flower  of  the  lily  family  with  disunited  petals. 
Star-of-Bethlehem  and  yucca  are  used  in  the  text.  Tulip,  trillium,  dog- 
tooth violet  (Erylhronium),  spiderwort  (Tradescantid),  white  lily,  all 
make  excellent  examples. 

282.  The  Floral  Envelopes.— Make  a  sketch  of  a  flower 
of  the  star-of-Bethlehem,  or  other  of  the  lily  tribe,  from 
the  outside.  Label  the  head  of  the  peduncle  that  sup- 
ports the  flower,  receptacle,  or  fonts,  the  three  outer 
greenish  leaves,  sepals,  the  three  inner,  lighter  colored 
ones,  petals.  The  sepals  taken  together  form  the  calyx, 


fped 

368  369  37° 

368-370.  —  Flower  of  a  hypogynous  monocotyledon  dissected:  368,  a  flower  of 
the  star-of-Bethlehem,  showing  the  different  sets  of  organs :  pet,  petals ;  sep,  sepals ; 
sta,  stamens :  pist,  pistil ;  ped,  peduncle ;  369,  side  view  of  star-of-Bethlehem  with  all 
the  petals  and  sepals  but  two  removed  to  show  order  of  the  parts :  r,  receptacle ; 
o,  ovary;  sty.  style;  stig,  stigma  —  parts  composing  the  pistil;  /  filament;  a,  anther 
—  parts  composing  the  stamen  ;  370,  cross  section  of  the  ovary  of  star-of-Bethlehem  : 
c,  c,  carpels;  ov,  ovules ;  pi,  placenta. 

and  the  petals,  the  corolla.  In  many  flowers,  such  as  the 
tulip  and  Atamasco  lily  (Zephyranthes\  there  is  little  or  no 
difference  between  them.  In  such  cases  the  calyx  and 
corolla  together  are  called  the  perianth,  but  the  distinc- 
tion of  parts  is  always  observed,  the  three  outer  divisions 
196 


HYPOGYNOUS   MONOCOTYLEDONS 


197 


being  regarded  as  sepals,  the  inner  ones  as  petals.  These 
two  sets  of  organs  constitute  the  floral  envelopes,  and  are 
not  essential  parts  of  the  flower,  as  it  can  fulfill  its  office 
of  producing  fruit  and  seed  without  them.  Note  their 
mode  of  attachment  to  the  receptacle  and  how  they  alter- 
nate with  each  other. 
Remove  one  of  the  se- 
pals and  one  of  the  <^\\\\\\^  F« 
petals,  and  notice  any 


371.  —  External  view  of  a  yucca 
blossom  :  br,  bract ;  pd,  peduncle ; 


372.  —  Vertical  section  of  yucca  whipplei : 
fed,  peduncle  ;  br,  bract ;  r,  receptacle ;  per, 
perianth  ;  sta,  stamen  ;  o,  ovary ;  sty,  style ; 
stg,  stigma.  The  last  three  parts  named 


r,  receptacle ;  s,  sepal ;  pet,  petal,      compose  the  pistil. 

differences  between  them  as  to  size,  shape,  or  color. 
Which  is  most  like  a  foliage  leaf  ?  Hold  each  up  to  the 
light  and  try  to  make  out  the  veining.  Is  it  the  same  as 
that  of  the  foliage  leaves  ?  How  many  of  each  are  there  ? 

283.  The  Essential  Organs.  —  Next  sketch  the  flower  on 
its  inner  face,  labeling  the  six  appendages  just  within  the 
petals,  stamens,  and  the  central  organ  within  the  ring  of 
stamens,  pistil.     These  are  called  essential  organs  because 
they  are  necessary  to  the  production  of  fruit  and  seed. 
Note  their  mode  of  insertion,  three  of  the  stamens  alter- 
nating with  the  petals  and  the  other  three  with  these,  and 
with  the  lobes  of  the  base  of  the  pistil. 

284.  The  Stamens.  —  Notice  whether  the   stamens  are 
all   alike,    or   whether   there   are   differences    as  to  size, 
height,  shape,  color,  etc.     Do  these  differences,  if  there 
are  any,  occur  indiscriminately  and  without  order,  or  in 
regular  succession  between  the  alternating  stamens  ?     Ex- 
amine one  of  the  little  powdery  yellow  bodies  at  the  tip 


198 


THE   FLOWER 


of   the  stamens,  and  see  whether  they  face  toward   the 
pistil  or  away  from  it.    In  the  first  case  they  are  said  to 

be  introrse,  in  the  second, 
extrorse. 

Observe  the  mode  of 
attachment  of  the  an- 
thers, whether  by  their 
base  merely  (terminal},  or 
through  their  entire  length 
(adnate),  or  to  the  tip  of 
the  filament  as  on  a  pivot, 
so  as  to  admit  of  their 
turning  freely  in  all  direc- 
tions (versatile). 

Remove  one  of  the  sta- 
mens and  sketch  it  as  it 
appears  under  the  lens, 


373    374  375  37&          377 

373-377-  —  Stamens   (GRAY):    373,    a 


and  opening  by  a  pore  at  the  apex. 


stamen  with  the  anther,  b,  surmounting 
the  filament,  a  (terminal),  and  opening  in 
the  normal  manner  down  the  outer  side 
of  each  cell ;  374,  stamen  of  tulip  tree,  with 
adnate  extrorse  anther ;  375,  stamen  of  an 
evening  primrose  ( CEnothera)  with  versa- 
tile anther;  376,  stamen  of  pyrola,  the 
anther  cells  opening  by  chinks  or  pores 
at  the  top;  377,  stamen  of  a  cranberry,  labeling  the  powdery  yel- 
with  the  anther  cells  prolonged  into  a  tube  IQW  body  ^  ^Q  ^  anf/ier> 

the  stalklike  (in  the  star- 
of-Bethlehem  expanded  and  petal-like)  body  supporting 
it,  filament.  Usually  the  filaments  are  threadlike,  whence 
their  name,  but  in  the  star-of-Bethlehem  they  look  like 
altered  petals,  and  frequently  a  stamen  is  found  in  a 
transition  state,  as  if  changing  from  stamen  to  petal, 
or  from  petal  back  to  stamen.  See  if  you  can  find  such 
a  one.  What  would  you  infer  from  this  fact  ? 

Notice  the  two  little  sacs  or  pouches  that  compose  the 
anther,  as  to  their  shape  and  manner  of  opening,  or  dehis- 
cing, to  discharge  the 
powder  contained  in 
them.  This  powder  is 
called  pollen^  and  will 
be  seen  under  the  lens 


378  379  380  301 

378-381.  — Forms  of  pollen  (GRAY):  378, 


tO  Consist  Of  little  yellow      from   mimulus   moschatus;   379,  sicyos ;   380, 

grains.      These    are    of    echin 

different  shapes,  colors,  and  sizes,  in  different  plants,  and 

the  surface  is  often  beautifully  grooved  and  striate.     The 


HYPOGYNOUS   MONOCOTYLEDONS 


199 


grains  with  their  markings  are  always  alike  in  the  same 
species,  so  that  it  is  possible  to  recognize  a  plant  by  its 
pollen  alone.  These  characters  are  generally  too  minute 
to  be  observed  without  a  compound  microscope,  but  in 
the  hibiscus,  and  some  others  of  the  mallow  family,  they 
can  be  distinguished  with  a  hand  lens. 

285.  The  Pistil.  —  Remove  the  stamens  and  sketch  the 
pistil  as  it  stands  on  the  receptacle.     Label  the  round  or 
oval  enlargement  at  the  base,  ovary,  the  threadlike  append- 
age rising  from  its  center,  style,  and  the  tip  end  of  the 
style,  stigma.     If  the  stigma  is  lobed  or  parted,  count  the 
divisions  and  see  if  there  is  any  correspondence  between 
them  and  the  number  of  petals  and  sepals,  or  of  the  lobes 
of  the  ovary.     Examine  the  tip  with  a  lens  and  notice  the 
sticky,  mucilaginous  exudation  that  moistens  it.     Can  you 
think  of  any  use  for  this  ?     If  not,  touch  one  of  the  pow- 
dery anthers  to   it,  and  examine  it  again  with  the  lens. 
What  do  you  see  ?  t 

286.  Pollination,  or  the   transfer   of   pollen   from   the 
anther  to  the  stigma,  is  a  matter   of   great   importance, 
as  the  pistil  can  not  develop  seed  without  it.     Note  the 
relative  position  of  pistils   and  stamens  and  see   if   it  is 
such  that  the  pollen  can  reach  the  stigma  without  external 
agency. 

287.  The  Ovary.  —  Observe 
the  shape  of  the  ovary,  and 
the    number    of    ridges,    or 
grooves  that  divide  the  sur- 
face.    These  lines  correspond 
to  the  sutures  of  the  fruit,  and 
show  of  how  many  carpels  the 
ovary   is    composed.      In  the 
star-of- Bethlehem    the   ovary 
has  six  sutures,  three  of  which 
represent  the  midrib   of   the 
carpellary   leaves,   and   three 


382, 383.  —  Ovary  of  yucca  aloifolia, 
a  hypogynous  monocotyledon,  dis- 
sected :  382,  vertical  section :  ov, 
ovules;  383,  diagram  of  a  horizontal 
section  of  the  same,  enlarged,  show- 
ing the  three  carpels  and  six  cells,  or 
loculi :  ds,  dorsal  sutures ;  vs,  ventral 
sutures ;  ov,  ovules ;  //,  placenta. 


200  THE   FLOWER 

the  inner  or  ventral  sutures,  so  that  there  are  only  three 
true  carpels.  Select  a  flower  that  has  begun  to  wither,  so 
that  the  ovary  is  well  developed,  cut  a  cross  section  near 
the  middle  and  try  to  make  out  the  number  of  cells,  or 
internal  divisions.  Make  an  enlarged  sketch  of  the  sec- 
tion as  it  appears  under  the  lens  (see  Fig.  383),  showing 
the  arrangement  of  the  parts,  also  a  longitudinal  section 
,(Fig.  382)  showing  their  relative  vertical  position.  Label 
the  little  round  bodies  that  represent  the  undeveloped  seeds 
ovules,  the  surface  to  which  they  are  attached,  placenta, 
and  the  cavities,  or  divisions  containing  them,  cells,  or 
loculi  (singular,  loculns}.  How  many  of  these  are  there  ? 
Compare  these  sketches  of  the  ovary  with  your  drawings 
of  dehiscent  fruits  in  Sections  93-109.  What  correspond- 
ences do  you  notice  between  them  ? 

As  the  ovary  is  merely  an  undeveloped  fruit,  and  the 
ovules  immature  seeds,  their  structure  is  the  same  as  that 
of  these  parts,  and  the  same  terms  are  used  in  describing 
them  (Sees.  73-79,  and  93-109). 

288.  Numerical  Plan.— Now  make  a  horizontal  diagram, 
after  the  model  given  in  Figure  384,  showing  the  manner  of 

attachment  of  the  different  cycles  —  sepals, 
petals,  stamens,  and  pistils,  the  number  of 
organs   in   each    set,  and    their    mode    of 
alternation  with  the  organs  of  the  other 
cycles.     Notice  that  in  the  star-of-Bethle- 
384  —Horizontal    ^em  and  similar  flowers,  the  parts  of  each 
diagram  of  a  flower    set  are  in  threes,   or  multiples   of  three. 

of    the    lily    kind.      TM-       •  n     ,      ,  -11  r      i 

The  dot  represents  Thls  ls  called  the  numerical  plan  of  the 
the  growing  axis  flower,  and  is  the  prevailing  number  among 
monocotyledons.  It  is  expressed  in  botani- 
cal language  by  saying  that  the  flower  is  trimerous,  a  word 
meaning  measured,  or  divided  off  into  parts  of  three. 

289.  Vertical  Order.  —  Next  make  a  vertical  diagram  of 
your  specimen  after  the  manner  shown  in  Figure  372,  and 
note  carefully  that  the  ovary  stands  above  the  other  organs 
(this  is  true  of  all  the  lily  family),  and  is  entirely  separate 


HYPOGYNOUS  MONOCOTYLEDONS 


201 


and  distinct  from  them.  In  such  cases  the  ovary  is  said 
to  be  free,  or  superior,  and  the  other  organs  inferior,  or 
hypogynous,  a  word  meaning  "inserted  under  the  pistil." 
These  terms  should  be  remembered,  as  the  distinction  is 
an  important  one  in  plant  evolution. 

290.  The  Flower  Bud.  —  Observe  the  manner  in  which 
the  sepals  and  petals  overlap  in  a  partly  unfolded  bud. 
Draw  a  diagram  rep- 
resenting their  posi- 
tion, as  in  Figures 
385-387-  Compare 
this  with  your  dia- 
grams of  leaves  and 


leaf    buds ;     does    it 
agree    with 
them,     and 


385-387.  —  Diagrams  of  three  modes  of  aestiva- 

agree      with      any      of     tion  common   among  monocotyledons:    385,  val- 
vate ;     386,    imbricate    (GRAY) ;     387,    convolute 
S0'      (GRAY). 

which  ?      Are    the 

parts  imbricated  or  valvate  ?     (Sees.  250,  256,  257.) 

The  arrangement  of  the  parts  of  the  flower  in  the  bud 
is  called  (estivation,  or  prefloration,  words  meaning  respec- 
tively "  summer  condition  "  and  "  condition  before  flower- 
ing." It  corresponds  to  the  vernation  of  leaf  buds,  and 
the  same  terms  are  used  in  describing  it. 

291.  Summary  of  Observations.  — In  the  flower  just  ex- 
amined we  found  that  there  were  four  sets  of  floral  organs 
present  —  sepals,  petals,  stamens,  and  pistil ;  that  the  indi- 
vidual organs  in  each  set  were  alike  in  size  and  shape ; 
that  there  were  the  same  number,  or  multiples  of  the  same 
number  of  parts  in  each  set,  and  that  all  the  parts  of  each 
set  were  entirely  separate  and  disconnected  the  one  from 
the  other,  and  from  those  of  the  other  cycles.  Such  a 
flower  is  said  to  be  :  — 

Perfect,  that  is,  provided  with  both  kinds  of  organs 
essential  to  the  production  of  seed  —  stamens,  and  pistil. 

Complete,  having  all  the  kinds  of  organs  that  a  flower 
can  have ;  viz. :  two  sets  of  essential  organs,  and  two  sets 
of  floral  envelopes. 


2O2 


THE   FLOWER 


Regular,  having  all  the  parts  of  each  set  of  the  same 
size  and  shape. 

Symmetrical,  having  the  same  number  of  organs,  or 
multiples  of  the  same  number  in  each  set. 

The  opposites  of  these  terms  are :  imperfect,  incom- 
plete, irregular,  and  asymmetrical,  or  unsymmetrical. 

Note  that  regularity  refers  to  form,  symmetry  to  number 
of  parts,  and  that  a  flower  may  be  perfect  without  being 
complete. 

EPIGYNOUS  MONOCOTYLEDONS 

MATERIAL.  —  Any  flower  of  the  iris  or  amaryllis  families.  Iris  is  used 
in  the  text.  Blackberry  lily  (Belatttfatula),  Atamasco  lily  (Zephyran- 
thes\  snowdrop,  daffodil,  narcissus,  etc.,  will  make  good  examples. 

292.  The  Perianth.  —  Compare  with  the  flower  last  ex- 
amined, a  common  flag,  or  iris.  Notice  that  the  latter  has 
no  peduncle,  but  is  sessile  in  the  axil  of  a  large,  membra- 
nous bract  called  a  spat  he.  Ob- 
serve also  that  the  lower  part  of 
the  perianth  is  united  into  a  long, 


ov* 

389.— Vertical  section  of  iris  flower  (after 
GRAY):  ov,  ovules;  pi,  placenta;  tu,  tube  of 
the  perianth  inclosing  the  style;  sta,  stamen; 
sti,  stigma. 

narrow  tube,  from  the  top  of  which 

the  Sfipals  and  p*als  e**nd as 

long,  curving  lobes.  Where  the 
parts  of  a  perianth  or  of  a  corolla  are  united  in  this  way, 
whether  throughout  their  whole  length,  as  in  the  morning- 
glory,  or  by  a  mere  thread  or  rim  at  the  base,  as  in  the 


EPIGYNOUS   MONOCOTYLEDONS  203 

water  pimpernel,  it  is  said  to  be  sympetalous,  meaning  "  of 
united  petals."  Monopetalous  and  gamopetalous  are  other 
words  used  to  denote  the  same  thing,  and  the  kindred 
terms,  synsepalous,  gamosepalous,  etc.,  are  applied  to  the 
calyx. 

293.  Dissection  of  the  Iris.  —  Sketch  the  outside  of  the 
specimen,  labeling  the  oblong,  three-lobed  enlargement  at 
the  base,  ovary,  the  prolongation  of  the  flower  above  it, 
tube  of  the  perianth,  the  three  outer  lobes  with  the  broad 
sessile  bases,  sepals,  the  others,  with  their  bases  narrowed 
and  bent  inward,  petals.  Now  turn  the  flower  over  and 
sketch  the  inside,  labeling  the  three  large,  petal-like  ex- 
pansions in  the  center,  stigmas.  Do  you  see  any  stamens  ? 
Remove  one  of  the  sepals  and  look  under  the  stigma; 
what  do  you  find  there  ?  Notice  the  little  honey  pockets 
at  the  foot  of  the  stamen.  Run  the  head  of  your  pencil 
into  them  and  see  what  would  happen  to  the  head  of  an 
insect  probing  for  honey. 

Remove  all  the  petals  and  sepals 
and  sketch  the  remaining  organs  in 
profile,  showing  the  position  of  the 
stamens.  Are  the  anthers  extrorse 
or  introrse  ?  What  is  their  mode 
of  dehiscence?  Remove  a  stamen 
and  sketch  it.  What  is  the  shape 
of  the  anther? 

_.  i         r      i  39°-  —  Vertical   section    of 

Remove   as   much   of   the   upper    irif   flower;  with   perianth 

part  of  the  perianth  tube  as  yOU  Can     removed,  showing  a  stamen 
...  .  .     ..  ,       .,       and  three  stigmas:   su,  stig- 

without  injuring  the  pistil,  and  with    matic  surface. 
a  sharp  knife,  slice  away  a  section 

down  through  the  ovary  so  as  to  show  the  long  style  and 
its  connection  with  the  placenta.  Make  a  sketch  of  this 
longitudinal  section  (see  Fig.  389),  labeling  the  long,  club- 
shaped  stalk  running  from  the  ovary  to  the  stigmas, 
style  ;  the  white  column  in  the  center  of  the  ovary  to  which 
the  undeveloped  seed  are  attached,  placenta,  and  the  unripe 
seeds,  ovules.  Notice  whether  the  placenta  is  central  or 


204 


THE   FLOWER 


391.  —  Cross  section  of 
ovary  of  iris  flower :  c,  c,  car- 
pels ;  /,  /,  cells,  or  loculi ;  ov, 
ovules ;  //.  placenta. 


parietal  (Sees.  103,  109).  Draw  a  cross  section  of  the 
ovary ;  how  many  cells  has  it  ?  Examine  with  a  lens  the 
little  flap  under  the  two-cleft  apex  of  one  of  the  stigmas,  and 
look  for  a  moist  spot  to  which  the 
pollen  will  adhere.  Label  this  in 
your  longitudinal  sketch,  stigmatic 
surface.  No  seeds  can  be  matured 
unless  some  of  the  pollen  reaches 
this  surface  ;  can  you  think  by  what 
agency  it  is  carried  there?  What 
insects  have  you  seen  hovering 
about  the  iris  ?  Notice  that  in  draw- 
ing his  head  out  of  the  flower,  an 
insect  would  not  touch  the  stig- 
matic surface,  since  it  is  on  the  upper  side  of  the  flap  and 
he  would  be  probing  tmdcr  it.  But  in  entering  the  next 
flower  that  he  visits,  he  is  likely  to  strike  his  head  against 
the  flap  and  turn  it  under,  thus  dusting  it  with  pollen 
brought  from  another  flower. 

Sketch  a  sepal  and  a  petal  separately,  and  note  their 
differences  as  to  shape,  color,  and  texture.  Hold  each  up 
to  the  light  and  observe  the  veining.  If  this  is  not  clear, 
stand  a  specimen  in  red  ink  for  two  or  three  hours  and 
examine  it  again.  Is  it  parallel  or  net  veined  ?  Can  you 
think  of  a  use  for  the  crest  of  hairlike  filaments  on  the 
upper  side  of  the  sepals  ? 

Examine  a  bud  in  cross  section.  Notice  how  the  sepals 
and  petals  overlap,  and  draw  a  diagram  of  the  section. 
This  manner  of  arrangement,  where  the  » 

outer  edge  of  one  piece  covers  the  inner  edge 
of  the  one  next  above  it  (Fig.  387),  is  said  to 
be  convolute.  Draw  diagrams  showing  the 
horizontal  and  vertical  arrangement  of  parts 
in  the  iris.  What  is  its  numerical  plan? 
Is  it  symmetrical  ?  Regular  ?  Are  the  parts 
all  free?  If  not,  which  are  united  among 


themselves   or  with  other  sets  of  organs? 
above  or  below  the  other  parts  ? 


302.  —  Horizon- 
tal diagram  of  iris 
flower. 

Is  the  ovarv 


DICOTYLEDONS 


205 


294.  The  Epigynous  Arrangement.  — In   cases   of   this 
kind,  where  the  other  organs  appear  to  rise  from  the  top  of 
the  ovary,  they  are  said  to  be  epigynous,  a  word  meaning 
"upon  the  ovary."     The  same  thing  is  expressed  in  a  dif- 
ferent way  by  saying  that  the  ovary  is  inferior,  or  that  the 
other  organs  are  superior.     To  make  the  matter  clear,  the 
two  sets  of  terms  employed  for  describing  the  position  of 
the  ovary  are  given  below  in  parallel  columns. 

Hypogynous  Epigynous 

Ovary  superior  Ovary  inferior 

Calyx  or  perianth  inferior      Calyx  or  perianth  superior 

The  epigynous  arrangement  is  considered  to  mark  a 
higher  stage  of  floral  development  than  the  hypogynous, 
which  is  characteristic  of  a  more  simple  and  primitive 
structure. 

DICOTYLEDONS 

MATERIAL. — Blossoms  of  any  convenient  specimens  of  the  mus- 
tard family.  Large  flowered  species  are  always  best  if  they  can  be 
obtained ;  cabbage,  mustard,  turnip,  and  wall-flower  are  very  good. 

Flowers  of  apple,  pear,  or  quince,  and  of  peach,  plum,  cherry,  or  rose  ; 
also  of  any  member  of  the  pea  family,  such  as  bean,  pea,  vetch,  black 
locust,  wistaria,  etc. 

295.  Dissection  of  a  Typical  Flower.  —  Gently  remove 
the  sepals  and  petals  from  a  mustard  or  other  cress  flower, 
lay  them  on  the  table  before  you  in  exactly  the  order  in 
which  they  grew  on  the  stem,  and  sketch  them.    How  many 
of   each  are  there,  and  how  do  they  alternate  with  one 
another  ?     Sketch  the  pistil  and  stamens  as  they  stand  on 
the  receptacle  ;  how  many  of  the  latter  are  there  ?     Notice 
that  two  of  the  six  are   outside   and   a  little  below   the 
others,  alternate  with  the  petals,  while  the  other  four  stand 
opposite  them,  as  is  natural  if  they  were  alternating  with 
another  ring  of  stamens  between  themselves  and  the  co- 
rolla.    Stamens  arranged  in  this  way  are  said  to  be  tetra- 
dynamous,  that  is,  four  stronger,  or  larger  than  the  others. 
Put  a  dot  before  two  of  the  sepals  in  your  first  drawing  to 


206 


THE   FLOWER 


indicate  the  position  of  the  two  outer  stamens,  and  a  cross 
before  the  other  two  to  show  where  stamens  are  wanting 
to  complete  the  symmetry  of  this  set  as  in  the  diagram 
(Fig.  395).  When  parts  necessary  to  complete  the  plan 
of  a  flower  are  wanting,  as  in  this  case,  they  are  said  to 
be  obsolete,  suppressed,  or  aborted.  Place  dots  before  the 
petals  to  represent  the  other  four  stamens. 

Examine  the  anthers  under  the  lens.  Are  they  extrorse 
or  introrse?  What  is  their  mode  of  attachment  to  the 
filament  ?  (Sec.  284.)  Sketch  one  of  the  anthers,  show- 


394  395 

393-396-  —  A  cruciferous  flower :  393,  side  view.  394,  view  from  above.  395, 
diagram  of  parts:  p,  petals;  s,  sepals;  st,  stamens;  pi,  pistil;  cl,  claw  of  petal ; 
+,  +,  position  of  the  missing  stamens.  396,  pistil  and  stamens,  enlarged  (GRAY) . 

ing  the  sagittate  base.  Remove  all  the  stamens  and 
sketch  the  pistil,  showing  the  long,  slender  ovary,  the  very 
short  style,  and  the  capitate  (round  and  knoblike)  stigma. 
Compare  the  pistil  with  a  more  matured  one  from  an  older 
flower  lower  down  on  the  stem,  and  with  the  descriptions 
of  dehiscent  fruits  in  Sections  93-109,  and  decide  to  which 
kind  it  belongs.  Represent  its  position  by  a  small  circle, 
in  the  center  of  your  sketch  of  the  separate  parts.  You 
have  now  a  complete  ground  plan  of  the  flower.  To  what 
form  of  leaf  arrangement  does  it  correspond  ?  Diagram 
a  vertical  section  showing  the  position  of  the  ovary  with 


DICOTYLEDONS 


207 


reference  to  the  other  parts,  and  report  in  your  notebook 
as  to  the  following  points :  — 

Numerical  plan  Presence  or  absence  of  parts 

Symmetry  Union  of  parts 

Regularity  Position  of  ovary 

A  flower  put  up  on  the  plan  of  four,  like  the  one  just 
examined,  is  said  to  be  tetramerous,  or  four  parted.  The 
cress  or  mustard  family  gets  its  botanical  name,  Crnciferce, 
cross-bearers,  from  the  four  opposite  petals,  which  have 
somewhat  the  appearance,  when  viewed  from  above,  of  a 
St.  Andrew's  Cross.  The  cruciferous  flowers  and  tetra- 
dynamous  stamens  are  striking  characteristics  of  this  fam- 
ily, which  is  so  well  marked  that  the  merest  beginner  can 
hardly  fail  to  recognize  any  member  of  it.  Notice  that 
its  flowers  belong  to  the  hypogynous  class. 

296.  Dissection  of  an  Epigynous  Dicotyledon.  —  Sketch  a 
blossom  of  quince,  haw,  pear,  or  apple,  first  from  the  out- 
side, then  from  the  inside, 
and  then  in  vertical  sec- 
tion, labeling  the  parts  as 
in  your  other  sketches. 
Notice  how  the  ovary  is 
sunk  in  the  hollowed- 
out  receptacle  (Sections 
74,  77).  Where  are  the 
other  parts  attached  ? 
Are  they  inferior  or  su- 
perior ?  Hold  up  a  petal 
to  the  light  and  exam- 
ine its  venation  through 
a  lens.  (Use  for  this 
purpose  a  petal  from  a 
flower  that  has  stood  in 
red  ink  for  two  or  three 
hours.  The  cherokee 
rose  petals  show  venation  beautifully.) 
veined  or  net  veined  ? 


397-400.  —  Flower  and  sections  of  pear: 
397,  cluster  of  blossoms,  showing  inflores- 
cence; 398,  vertical  section  of  a  flower; 
399,  ground  plan  of  a  flower;  400,  vertical 
section  of  fruit. 


Is   it   parallel 


20g  THE   FLOWER 

Remove  a  stamen  and  sketch  it  as  it  appears  under  the 
lens.  Notice  the  attachment  and  shape  of  the  anthers. 
Are  they  all  of  the  same  color  ?  How  do  you  account  for 
the  difference,  if  there  is  any?  Is  the  position  of  the 
pistil  and  stamens  such  that  the  pollen  from  the  anthers 
can  readily  reach  the  stigmas  without  external  aid? 
Examine  the  pistil  in  flowers  of  different  ages,  and  see  if 
the  stigma  is  mature  (that  is,  moist  and  sticky)  at  the 
same  time  that  the  anthers  are  discharging  their  pollen. 

Draw  a  cross  section  of  the  ovary  and  try  to  make  out 
with  a  lens  the  number  of  cells,  or  loculi.     If  you  can  not 
succeed,  turn  to  the  cross  section  of  the  pome  made  in  your 
study  of  fruits,  and  that  will  settle  the  question,  since  the 
Q  £  fruit  is  merely  a 

ripened  ovary. 

Examine     the 
overlapping     of 
the  petals  in  the 
4oi  02  bud»  and  diagram 

401-403.  —  Types    of    imbricated    aestivation    common     their       aestivation 
among  dicotyledons  (after  GRAY). 


Compare  this  with  the  diagrams  of  leaf  arrangement  in 
Sections  50-52,  and  decide  to  which  it  corresponds. 

Diagram  the  plan  of  the  flower  in  cross  and  vertical 
section.  How  many  parts  are  there  in  each  set  ?  Can  you 
readily  tell  the  number  of  stamens  ?  When  the  individuals 
of  any  set  or  cycle  of  organs  are  too  numerous  to  be  easily 
counted,  like  the  stamens  of  the  apple,  pear,  and  peach, 
or  the  petals  of  the  water  lily,  they  are  said  to  be  indefinite. 
It  is  very  seldom  that  perfect  symmetry  is  found  in  all 
parts  of  the  flower.  The  stamens  and  pistil,  in  particular, 
show  a  great  tendency  to  variation,  so  that  the  numerical 
plan  is  generally  determined  by  the  calyx  and  corolla. 
Where  the  parts  are  in  fives,  as  in  the  pear,  quince,  wild 
rose,  etc.,  the  flower  is  said  to  be  pentamerous,  or  in  sets  of 
five. 

After  drawing  the  diagrams,  write  in  your  notebook 
answers  to  the  following  questions  :  — 


DICOTYLEDOxNS 


209 


What  is  the  numerical  plan  of  the  flower  ? 
Which  of  its  circles  of  organs  is  lacking  in  symmetry  ? 
Which  sets  of  organs  are  adherent  to  other  sets? 
Is  the  flower  epigynous  or  hypogynous  ? 

297.  Examination  of  a  Perigynous  Flower.  —  Compare 
with  the  specimen  just  examined,  a  blossom  of  peach, 
almond,  plum,  or  cherry.  Is  its  nu- 
merical plan  the  same?  Make  a  dia- 
gram showing  the  arrangement  of 
parts  in  vertical  section.  Is  the  calyx 
inferior  or  superior  ?  Where  are  the 
petals  and  stamens  inserted  ? 

Flowers  of  this  kind,  where  the 
ovary  is  free  and  the  other  parts 
attached  to  a  prolongation  of  the  recep- 
tacle containing  it,  are  said  to  be 


404.  —  Vertical  section 
of  an  almond  blossom 
with  petals  removed, 

perigynous,  meaning  "  around  the  pis-    showing  the  perigynous 
til."      It   is   intermediate   between  the    a 
hypogynous     and     epigynous     arrangement,     sometimes 
approaching   more   nearly  to  the   latter,  as   in  the  rose, 
sometimes  remaining  clearly  of  the  hypogynous  type,  as 


405  406  407 

405-407.  — Diagrams  showing  arrangement  of  parts  (bd,  receptacle;  k,  calyx; 
kr,  corolla;  st,  stamens;  fr,  ovary;  g,  style;  »,  stigma):  405,  perigynous;  406, 
hypogynous ;  407,  epigynous. 

in  the  peach  and  cherry.  In  general  a  flower  is  not  con- 
sidered epigynous  unless  the  ovary  is  more  or  less  con- 
solidated with  the  parts  around  it. 

ANDREWS'S  EOT.  —  14 


210 


THE   FLOWER 


298.  Dissection  of  an  Irregular  Flower.  —  Irregularity 
is  more  noticeable  in  the  corolla  than  in  the  other  parts, 
and  when  we  speak  of  an  irregular  flower  the  reference  is 
generally  to  that  organ. 

Sketch  a  blossom  of  any  kind  of  pea  or  vetch  as  it 
appears  on  the  outside.  Are  the  sepals  all  of  the  same 
length  and  shape  ?  If  not,  which  are  the  shorter,  the 
upper  or  lower  ? 

Turn  the  flower  over  and  examine  its  inner  face. 
Notice  the  large,  round,  and  usually  upright  petal  at  the 
back,  the  two  smaller  ones  on  each  side,  and  the  boat- 


408-412.  —  Dissection  of  papilionaceous  flowers  (after  GRAY)  :  408,  front  view 
of  a  corolla.  409,  the  petals  displayed :  v,  vexillum,  or  standard  ;  w,  wings;  k,  keel. 
410,  side  view  with  nil  except  one  of  the  lower  petals  removed,  showing  the  essential 
organs  protected  in  the  keel:  /,  loose  stamen;  st,  stamen  tube.  411,  side  view, 
showing  how  the  anthers  protrude  when  the  keel  is  depressed.  412,  ground  plan. 

shaped  body  between  them,  formed  of  two  small  petals 
more  or  less  united  at  the  apex.  Press  the  side  petals 
gently  down  with  the  thumb  and -forefinger  and  notice 
how  the  essential  organs  are  forced  out  from  the  little  boat 
in  which  they  are  concealed.  Observe  how  the  end  of  the 
style  is  bent  over  so  as  to  bring  the  stigma  uppermost 
when  the  petals  are  depressed.  Imagine  the  legs  of  a 
bee  or  a  butterfly  probing  for  honey ;  with  what  organ 
would  his  body  first  come  in  contact  when  he  alighted  ? 
If  his  thorax  and  abdomen  had  previously  become  dusted 
with  pollen  when  visiting  another  flower,  where  would  the 
pollen  be  likely  to  be  deposited  ? 

Remove  the  sepals  and  petals  from  one  side  and  sketch 


DICOTYLEDONS  211 

the  flower  in  longitudinal  section,  showing  the  position  of  the 
pistil  and  stamens.  Then  remove  all  the  petals,  and  spread 
in  their  natural  order  on  the  table  before  you,  and  sketch 
as  they  lie  (Fig.  409).  Label  the  large,  round  upper  one, 
vexillum,  the  smaller  pair  on  each  side,  wings,  and  the  two 
more  or  less  coherent  ones  in  which  the  pistil  and  stamens 
are  contained,  keel.  Corollas  of  this  kind  are  named  papili- 
onaceous, from  the  Latin  word  papilio,  a  butterfly,  on  ac- 
count of  their  general  resemblance  to  that  insect ;  while  the 
old  names  are  somewhat  incongruous,  they  are  descriptive, 
and  answer  their  purpose  sufficiently  well  to  be  retained. 

299.  Dissection  (continued}.  —  Count  the  stamens,  and 
notice  how  they  are  united  into  two  sets  of  nine  and  one. 
Stamens  united  in  this  way,  no  matter  what  the  number  in 
each  set,  are  said  to  be  diadelpJious,  that  is,  in  two  brother- 
hoods.    Notice  the  position  of  the  lone  brother,  whether 
below  the  pistil  —  next  to  the  keel  —  or  above,  facing  the 
vexillum.     Would  the  projection   of  the  pistil  when  the 
wings  are  depressed  be  facilitated  to  the  same  extent  if 
the  opening  in  the  stamen  tube  were  on  the  other  side,  or 
if  the  filaments  were  monadelphous — all  united  into  one 
set  ?     Flatten  out  the  stamen  tube,  or  sheath  formed  by 
the  united  filaments,  and  sketch  it. 

Remove  all  the  parts  from  around  the  pistil,  and  sketch 
it  as  it  stands  upon  the  receptacle.  Look  through  your 
lens  for  the  stigmatic  surface  (Sec.  293).  See  if  there  are 
any  hairs  upon  the  style,  and  if  so,  whether  they  are  on 
the  front,  the  back,  or  all  around.  Can  you  think  of  a 
use  for  these  hairs  ? 

300.  Dissection  (continued}.  —  Notice  how  the  long,  nar- 
row ovary  is  attached  to  the  receptacle;  is  it  sessile,  or 
raised  on  a  short  footstalk  ?     If  the  latter,  label  the  foot- 
stalk stipcl.     Select  a  well-developed  pistil  from  one  of  the 
lower  flowers,  open  the  ovary  parallel  with  its  flattened 
sides  and  sketch  the  two  halves  as  they  appear  under  the 
lens.     Notice  to  which  side  the  ovules  are  attached,  the 
upper  (toward  the  vexillum)  or  the   lower,   and  label   i> 


212  THE  FLOWER 

placenta.  Which  suture  of  the  pod  is  this  (Sec.  98)? 
Compare  with  your  sketches  of  dehiscent 
fruits ;  which  one  does  it  resemble  ? 

Examine  a   bud  and   diagram  the   aesti- 
vation.    Which  petal  overlaps  the  others? 
Diagram  the  flower  in  horizontal  and  ver- 
papiiionaceous    tical  section,  and  decide  upon  the  following 

points :  - 

What  is  the  numerical  plan  ? 

In  what  organ    or  organs  is   there   a   departure   from 
symmetry  ? 

In  which  is  there  irregularity  ? 

Are  all  the  parts  free  ? 

In  which  set  of  organs  is  there  union  ? 

Is  the  flower  hypogynous  or  epigynous  ? 

301.  Significance  of  these  Distinctions. — These  distinc- 
tions are  important  to  remember  not  only  because  they  are 
very  useful  in  grouping  and  classifying  plants,  but  because 
they  mark  successive  stages  in  the  evolution  of  the  flower. 
In  general,  flowers  of  a  primitive  type  and  less  advanced 
organization  are  characterized  by  having  their  organs  free 
and  hypogynous,  while  the  more  highly  developed  forms 
show  a  tendency  to  consolidation  and  union  of  parts,  and 
the  epigynous  mode  of  insertion.     Irregularity  also,  since 
it  indicates  specialization  and  adaptation  to  a    particular 
purpose,  may  be  regarded  as  a  mark  of  advanced  evolution. 

302.  Numerical  Plan  of  Dicotyledons.  —  In  all  the  flowers 
examined  in  Sections  295-300  except  the  first  specimen, 
the  organs  were  found  to  be  in  fives,  or  multiples  of  five. 
This  is  the  prevailing  number  among  dicotyledons,  though 
other  orders  are  not  uncommon,   and   occasionally  even 
trimerous  forms  like  the  magnolia,  pawpaw,  etc.,  are  met 
with.      In   the    mustard    family,    in   the    common    yellow 
primroses  of   our  old  fields,   and   in    several   other  well- 
known  species,  the  tetramerous,  or  fourfold  arrangement 
prevails,  while  some  of  the  saxifrages,  and  a  few  other 
plants  are  dimeroits,  having  their  parts  in  twos.     For  the 


THE   COROLLA 


213 


sake  of  brevity  these  terms  are  generally  written,  in  botani- 
cal descriptions,  2merous,  smerous,  4merous,  smerous, 
which  are  pronounced  respectively,  dimerous,  trimerous, 
tetramerous,  and  pentamerous. 

THE  COROLLA 

MATERIAL.  —  Practical  illustrations  of  Sections  303-318  must  be 
sought  for  out  of  doors,  by  observing  the  various  flowers  and  weeds 
'with  which  the  student  comes  in  contact  in  his  daily  walks. 

303.  Cohesion  and  Adhesion.  —  A  flower  that  is  perfectly 
symmetrical  and  regular,  with  all  its  parts  free  and  distinct, 
like  the  star-of-Bethlehem  and  most  of  the  lily  family,  is 
not  often  met  with.     Frequently  one  or  more  of  the  organs 
are  wanting  ;  more  frequently  still  they  are  combined  and 
consolidated   in   various   ways   with    each   other   or   with 
organs  of  a  different  set.     Union  between  organs  of  the 
same  set  is  called  cohesion;  between  organs  of  different 
kinds,   adhesion,  or  actuation.     The  opposite  of  coherent 
is  distinct  ;  of  adherent, 

free, 

304.  Apopetalous    and 
Sympetalous  Corollas.— 
Consolidation  may  occur 
between  any  parts  of  the 
flower,  either  of  the  same 
or  of   different  sets,  but 
is    more    conspicuous   in 
the  corolla,  so   that  this 
character  has  been  made 
the  basis  of  one  of  the 
great   divisions   of   seed- 
bearing  plants,  which  are 
classed  as  apopetalous  and 
sympetalous,  according  as 

their  Corollas  are  COm- 
posed  of  separate  Or  Of 
United  petals.  Flowers 
that  have  no  Corolla  are 


416  419 

4  14-419-  -Irregular  apopetalous  corollas 
(afttr  GRAY)  :  414,  a  larkspur  flower;  415, 
sepals,  s,  s,  and  petals,  p,  p.  displayed  ;  416, 
diagram  of  arrangement  ;  417,  corolla  of  the 
violet;  418,  sepals  and  petals  displayed; 
419.  diagram  of  arrangement. 


214 


THE   FLOWER 


said  to  be  apetalous,  that  is,  without  petals.     The  terra 
polypetalous  is  sometimes  used  instead  of  apopetalous. 

305.  Apopetalous  Corollas  may  have  any  number  of 
petals,  from  one  or  two,  as  in  the  enchanter's  nightshade 
(Circ(za),  to  the  indefinite  whorls  of  such  double  flowers 
as  the  cactus  and  water  lily.  They  may  be  of  all  shapes 
and  sizes,  and  sometimes  present  the  greatest  irregularities 
of  structure,  as  the  violet,  tropaeolum,  larkspur,  and  colum- 
bine. The  commonest  type  of  irregular  corolla  belonging 
to  the  apopetalous  group,  and  the  only  one  that  has  received 
a  special  name,  is  the  papilionaceous  corolla  already  de- 
scribed, that  characterizes  the  pea  family.  This  may  well 
be  called  the  reigning  family  of  this  division,  since  it  is 
by  far  the  most  important  and  numerous,  containing  about 
seven  thousand  known  species,  among  which  are  many  of 
our  most  useful  food  plants. 


420-425.  —  Forms  of  sympetalous  corollas  (420-422,  and  425,  after  GRAY)  : 
420,  rotate  corolla  of  nightshade;  421,  salver-shaped  corolla  of  phlox;  422,  cam- 
panulate  corolla  of  harebell ;  423,  urceolate,  or  urn-shaped  corolla  of  andromeda ; 
424,  tubular  corolla  of  spigelia ;  425,  funnel-shaped  corolla  of  morning-glory. 

306.  Sympetalous  Corollas  are  of  so  many  different  forms 
that  it  has  been  found  convenient  to  apply  special  names 
to  the  more  important  of  them.  A  correct  idea  of  these 
can  be  gained  by  comparing  living  specimens  as  they  are 
found  with  Figures  420-425. 


THE   COROLLA 


215 


307.  The  Ligulate,  or  strap-shaped  corolla,  seen  in  the 
rays  of  the  sunflower  family,  is  of  such  frequent  occurrence 
as  to  deserve  a  special  examination.  If 
you  will  remove  one  of  the  small  blos- 
soms from  the  disk  of  any  large  composite 
flower  (Fig.  426) 
and  imagine  its 
corolla  greatly  en- 
larged and  split 
open  on  the  inner 
side,  you  will  get 

a  very  good  idea  of  426.  — A  head  of  artichoke  427."^  A  ray  flower  of 
the  nature  of  the  flower  divided  lengthwise.  artichoke,  enlarged. 

rays.  The  five  little  teeth  into  which  it  is  usually  cleft 
at  the  top  show  the  number  of  lobes  or  petals  of  which 

it  is  composed.  The  corolla  of  the  lobelia 
St..  ^f^  ysstv-?t  represents  an  intermediate  state  between 

the  tubular  and  ligu- 

& T  late  forms  (Fig.  429). 


308.  Bilabiate  Co- 
rollas. —  By  far  the 
most  important  and 
widely  distributed  of 
sympetalous  corollas 
is  the  bilabiate,  or 
two-lipped  kind,  dis- 
tinctive of  the  mint 


428.  — A  vertical 
section  of  a  disk  flower, 
showing  the  divided 
style,  st,  and  the  sta- 
mens, s,  s,  with  their 
anthers  united  (syn- 
genesious) . 


429.  —  Flower  of  Lobelia 
cardinalis,   with    tube    of 


corolla    divided    on    one  d    figwort    families 

side;    filaments   and    an- 

thers united  into  a  tube 

(after  GRAY)  :  /  tube  of 
filaments;  a,  anthers. 


and  their  allied 
groups,  numbering  in 
all  over  six  thousand 
known  species.  They  are  of  many  varieties,  from  the 
scarcely  perceptible  irregularity  of  the  verbena  and  mullein 
to  the  complicated  structures  of  the  sage,  snapdragon,  and 
toad  flax.  Two  of  them  are  so  strongly  marked  that 
they  have  received  special  names.  These  are  the  ringent, 
or  open-mouthed,  and  the  personate,  or  closed  (Figs.  430 


2i6  THE   FLOWER 

and  431),  so  called  from  a  fancied  resemblance  of  the 
swollen  palate  to  a  grotesque  persona,  or  mask.  The  sage 
and  dead  nettle  are  familiar  examples  of  the  first,  the 
snapdragon  and  toadflax  of  the  second.  An  inspection 
of  the  sage  or  the  dead  nettle  will  show  that  the  two 
lips  represent  the  divisions  of  a  five-lobed  sympetalous 
corolla  united  into  sets  of  two  and  three  petals  respectively. 
The  very  divergent  appendage  of  the  lower  lip  represents 
the  middle  one  of  three  petals,  while  the  two  lateral  ones 
have  become  greatly  reduced,  or  in  the  dead  nettle,  nearly 


43°  431  432  433 

430-433.  —  Bilabiate  corollas:  430,  personate  flower  of  snapdragon  (after  GRAY)  ; 
431,  ringent  corolla  of  dead  nettle;  432,  front  view;  433,  horizontal  diagram. 

obsolete.  The  arched  upper  lip  represents  two  petals  con- 
fluent into  one,  a  notch  in  many  species  (catnip,  dittany, 
snapdragon),  indicating  the  original  line  of  division. 

Some  of  the  names  given  to  sympetalous  corollas  apply 
equally  to  apopetalous  ones.  Chickweed  and  moonseed 
are  rotate ;  the  uvularias,  the  yucca,  and  the  abutilon  of 
the  greenhouses  are  bell-shaped,  or  campanulate ;  okra 
and  some  of  the  lilies  are  funnel-shaped. 

The  same  terms  that  are  used  in  describing  the  shapes 
of  foliage  leaves  are  applied  to  the  sepals  and  petals  of 
flowers. 

SUPPRESSIONS,  ALTERATIONS.  AND  APPENDAGES 

MATERIAL  is  to  be  sought  for  out  of  doors,  wherever  it  may  present 
itself.  Specimens  of  pine,  oak,  or  other  unisexual  flowers  should  be 
provided  for  class  study.  If  these  are  not  in  season,  the  mulberry, 
Osage  orange,  hop,  sycamore,  black  gum,  peisimmon,  and  the  gourds, 
squashes,  and  melons,  furnish  good  examples  of  unisexual  flowers,  one 
or  more  of  which  ought  to  be  examined. 


SUPPRESSIONS,   ALTERATIONS,   APPENDAGES      2 1/ 


435.  —  Petal-like  sepals 
of  clematis. 


309.  Undeveloped  Organs.  —  A  flower  may  depart  from 
the  normal  type  either  by  the  non-development  of  parts, 
or  through  the  suppression  or  alteration  of 

parts  already  developed.  A  want  of  develop- 
ment generally  characterizes  simple  and 
primitive  forms  such  as. the  naked  flowers 
of  the  lizard's  tail  (Saurtmes),  the  black  ash, 

and  willow,  in  which   the    ft£J  oTSJ 

floral  envelopes  are  entirely    rurus    (after 
...  '     GRAY). 

lacking,    or   reduced    to    a 

mere  scale  or  bract.  A  step  higher  in 
the  order  of  development  the  floral  envel- 
opes appear,  but  are  usually  inconspic- 
uous and  without  differentiation  into 
calyx  and  corolla,  as  in  the  elm,  knot- 
weeds,  docks,  etc.  Where  only  one  set  of  these  organs  is 
present,  it  is  considered  a  calyx,  no  matter  how  large  and 
conspicuous  it  may  be,  as  in  the  four-o'clock,  and  clematis. 

310.  Unisexual  Flowers.  —  Where  one  of  the  essential 
organs  is  lacking,  the  flower  is  unisexual,  which  means  that 
either  stamens  only,   or  pistils  only,   occur  in  the  same 
flower.     When  the  stamens  alone  are 

present  the  flower  is  said  to  be  stam- 
inate,  or  sterile  because  it  is  incapable 
of  producing  seeds  of  its  own,  though 
its  pollen  is  a  necessary  factor  in  their 
production.  If,  on  the  other  hand,  the 
ovary  is  present  and  the  stamens 
absent,  the  flower  is  pistillate  and  fer- 
tile ;  that  is,  capable  of  producing  fruit 
when  impregnated  with  pollen.  Some- 
times both  stamens  and  pistils  are 
wanting,  as  in  the  showy  corollas  of 
the  garden  "  snowball "  and  hydrangea,  and  the  rays 
of  the  sunflower.  Such  blossoms  are  said  to  be  neutral, 
from  the  Latin  word  neuter,  neither,  because  they  have 
neither  pistils  nor  stamens.  They  can,  of  course,  have  no 


436  437 

436,  437.  —  Flowers  of 
willow  :  436,  pistillate  ; 
437,  staminate. 


218 


THE   FLOWER 


direct  part  in  the  production  of  fruit,  but  are  for  show 
merely.  Their  show,  however,  is  far  from  being  a  vain  and 
empty  one,  as  we  shall  see  in  Sections  330-338. 

311.  Monoecious  and  Dioecious  Plants.  —  When  both 
kinds  of  flowers,  staminate  and  pistillate,  are  borne  on  the 
same  plant,  as  in  the  oak,  pine,  "hickory,  and  most  of  our 
common  forest  trees,  they  are  said  to  be  monoecious,  a 
word  which  means  "belonging  to  one  household,"  and 
dioecious,  or  "  of  two  households,"  when  borne  on  separate 
plants,  as  in  the  willow,  sassafras,  and  black  gum.  Draw 
a  flowering  twig  of  oak,  or  other  amentaceous  (ament- 
bearing)  tree.  Where  are  the  fertile  flowers  situated  ? 
Notice  how  very  much  more  numerous  the  staminate 
flowers  are  than  the  fertile  ones. 

312.  Advantages  of  the  Uni- 
sexual Arrangement.  —  The  ab- 
sence of  parts  in  a  flower  is  not 
necessarily  a  mark  of  low  organ- 
ization, but  may  be  the  result  of 
adaptation  to  its  surroundings. 
It  has  been  proved  by  experi- 
ment that  flowers  will  gener- 
ally produce  more  vigorous  and 
healthy  seed  when  impregnated 
with  pollen  from  a  different 

438.— Twig  Of   oak  with  both  .               ... 

kinds  of  flowers  .-/fertile  flowers;  plant    of    the    Same  SpCClCS,  and 

s,  s,  staminate;  a,  pistillate  flower,  unisexual   flowers   promote  this 

enlarged;     b,    vertical    section    of  L 

pistillate  flower,  enlarged;    c,  por-  TCSUlt   by  making    it    impossible 

tion  of  one  of  the  sterile  aments  for  any  bloSSOm   to   receive  pol- 

enlarged,   showing  the  clusters   of  J 

stamens.  len  from  itself. 

313.  Suppression  or  Abortion  of  Organs.  —  Sometimes 
this  advantage  is  secured  by  the  suppression  of  one  or  the 
other  set  of  organs  in  different  flowers.  In  the  pistillate 
flowers  of  the  persimmon  the  aborted  stamens  are  quite 
conspicuous,  though  entirely  sterile,  producing  not  a  grain 
of  pollen.  Rudimentary  (undeveloped)  organs  of  this  kind 


SUPPRESSIONS,   ALTERATIONS,   APPENDAGES      219 


are  very  common  and  are  a  frequent  cause  of  irregularity 
and  want  of  symmetry,  as  was  seen  in  the  stamens  of  the 
cress  family  (Sec.  295).  Suppressed  stamens  are  a  com- 
mon characteristic  of  the  great  bilabiate  group  (Sec.  308), 
large  numbers  of  species  having  only  two  or  four,  but 
these  are  often  accompanied^  as  in  the  pentstemon,  che- 
lone,  and  figwort,  by  sterile  filaments  in  a  more  or  less 
aborted  condition  that  carry  out  the 
law  of  symmetry  indicated  in  the  five- 
lobed  corolla  (Sec.  308).  The  fila- 
ment and  style  are  often  wanting,  so 
that  the  anther  or  the  stigma  becomes 
sessile.  While  it  is  usual  to  speak  of 
the  stamens  and  pistil  as  essential 
organs,  it  is  really  only  the  ovary  and 
the  anther,  or  more  strictly  speaking, 
the  ovules  and  pollen  that  are  absolutely 
essential.  The  style  is  merely  an  ap- 
pendage for  placing  the  stigma  where 
it  will  be  brought  more  easily  into  con- 
tact with  the  pollen,  and  may  be  of  any 


440 

439,    440.  —  Abortive 
stamens   {after  GRAY)  : 

length,  from  a  foot  or  more,  as  in  the    439.coroiiaof/>«i*/««<». 

~.  p  _     ,.  grandiflorus  laid    open, 

"silk      of  the  Indian  corn,  to  a  mere    with  its  four  stamens,  and 

a  sterile  filament  in  the 
place  of  the  fifth  stamen ; 
440,  corolla  of  catalpa 
laid  open,  with  two  per- 
fect stamens  and  the 
vestiges  of  three  abortive 
ones. 


line,  or  entirely  absent,  as  in  the  poppy 
and  some  of  the  yuccas. 

The  study  of  these  rudimentary  or 
discarded  organs  helps  to  explain  many 
deviations  in  the  structure  of  flowers 
that  would  otherwise  be  very  puzzling,  and  by  their  aid 
we  can  often  reconstruct  the  plan  of  a  flower  that  seems 
to  have  lost  all  conformity  to  the  type. 

314.  Cleistogamic  (closed}  Flowers  are  so  called  because 
they  never  unfold,  but  are  pollinated  in  the  bud.  Common 
examples  are  the  inconspicuous  closed  flowers,  on  very 
short  peduncles,  concealed  under  the  leaves  of  most 
violets.  Sometimes,  as  in  the  fringed  polygala,  they  are 
borne  on  underground  stems  and  never  rise  above  ground  at 


220 


THE   FLOWER 


441.  —  Staminodia,  transformed  sta- 
mens of  canna  stimulating  petal's :  pet, 
petals ;  sf,  Staminodia. 


all.  The  corolla  is  usually  wanting  and  the  stamens  and 
pistil  are  greatly  reduced,  but  they  are  much  more  prolific 
than  ordinary  blossoms. 

315.   Transformations. —  Instead  of  suppression,  organs 

frequently  undergo  an  alteration  into  something  else  by 
which  their  nature  is  greatly 
obscured.  Conspicuous  in- 
stances are  the  brilliant  Stam- 
inodia, or  altered  stamens  of 
the  canna,  that  simulate 
petals  (Fig.  441),  and  the  four 
large  white  bracts,  usually 
mistaken  for  a  corolla,  that 
surround  the  flower  clusters 
of  the  dog- 
wood. In  the 
cereus  and 

other  cactuses,  bracts  may  be  found  in  all 

stages  of  transition,  from  spines  or  scales 

to  the   most   gorgeous  of   corollas.     The 

rose,  camellia,  and  water  lily  furnish  other 

instances  of  the  same  kind ;  and  in  fact, 

examples  of  the  transition  of  almost  any 

organ  into  another  may  be  observed  by 

one  who  will  take  the  trouble  to  look  for 

them. 

316.   Appendages  of  the  Corolla.  —  An 

appendage  attached  to  the  inner  face  of 
the  corolla,  like  the  funnel-shaped  or  bell- 
shaped  projection  within  the  perianth  of  442.  — Flower  of  a 

jrrj-i  j     •  .1  i          i  r      i          cactus  (cereus  greg- 

daffodils  and  jonquils  and  others  of  the    fu)t  showing  tran- 
amaryllis  family,  to  which  they  belong,  is    sition  from  scales  to 

petals. 

called  a  crown.     It  is  no  part  of  the  peri- 
anth proper,  and  does  not  interfere  in  any  way  with  the 
symmetry  of  the  flower.     The  crown  of  the  passion  flower, 
to  which   so  much  of   its  beauty  is  due,  is  composed  of 
a  ring  of  abortive  filaments,  brilliantly  colored,  that  sur- 


SUPPRESSIONS,   ALTERATIONS,   APPENDAGES      221 

round  the  base  of  the  style.  In  the  milkweed  (Asclepias} 
the  crown  itself  is  appendaged  with  five  little  incurved 
horns. 

317.  Other  Appendages.  —  Though  appendages  are  most 
frequently  connected  with  the  calyx  and  corolla,  they  may 
attach  to  any  part  of  the  plant.     Figure  377   shows   an 
appendaged   anther;   and  the  various  appliances  for  dis- 
persal furnish  examples  of  appendaged  fruits  and  seeds. 
When  the  appendage  is  so  large  as  to  inclose  a  whole 
seed,  like  the  loose  transparent  sac  around  the  seed  of  the 
water  lily,  and  the  brilliant  scarlet  pulp  around  the  seeds 
of  the  strawberry  bush  (Evonymous  americanus),  it  is  called 
an  aril ;  can  you  think  of  a  use  for  it  ? 

318.  Use  of  Appendages.  —  The  offices  of  these  append- 
ages are  as  varied  as  the  appendages  themselves.     They 
may  be,  as  in  the  case  of  hairy  filaments,  to  protect  the 
pollen  from  crawling  insects ;  to  keep  out  rain,  dew,  or 
frost ;  to  retain  or  to  shed  moisture ;  to  secrete  honey,  as 
in  the  spurs  and  sacs  of  the  violet  and  larkspur,  or  in 
other  ways  to  attract  and  repel  insects  that  aid  or  hinder 
the  dispersal  of  pollen.     As  they  are  generally  the  result 
of  special  adaptations  on  the  part  of  the  plant  to  its  sur- 
roundings —  more  particularly  with  regard  to  insect  polli- 
nation —  they  are  usually  indicative  of  an  advanced  stage 
of  floral  development. 

PRACTICAL  QUESTIONS 

1 .  Why  does  a  strawberry  bed  sometimes  fail  to  fruit  well,  although  it 
may  flower  abundantly?     (310,311.) 

2.  Are    berries   found   on   all   sassafras   trees?   on  all  buckthorns? 
hollies? 

3.  Would  a  solitary  hop  vine  produce  fruit?  A  solitary  ash  tree? 

4.  Why  is  a  mistletoe  bough  with  berries  on  it  so  much  harder  to 
find  than  one  with  foilage  merely?     (310,  311.) 

5.  Explain  the  nature  and  use  of  the  appendages  in  such  of  the  plants 
named  below  as  you  can  obtain ;  crown  of  the  maypop,  jonquil,  milk- 
weed ;  spurs  of  the  columbine,  tropaeolum,  jewel  weed,  etc. ;  bracts  of  the 
dogwood  and  poinsettia ;  spathe  of  Jack-in-the-pulpit  and  other  arums. 


222  THE   FLOWER 

NATURE  AND  OFFICE   OF  THE  FLOWER 

MATERIAL.  —  Any  kind  of  large  flower  may  be  used  ;  those  of  the 
hollyhock,  okra,  cotton,  hibiscus,  or  others  of  the  mallow  family  are 
recommended,  as  their  pollen  grains  are  large  enough  to  be  observed 
fairly  well  with  a  hand  lens.  The  cultivated  Syrian  hibiscus  is  the  one 
used  in  the  text. 

319.  Flower  and  Leaf.  —  We  have  seen  that  the  vena- 
tion of   petals  and  sepals  corresponds  in  a  general  way 
with  that  of  foliage  leaves  of  the  class  to  which  they  be- 
long, and  that  their  arrangement  around  their  axis  is  analo- 
gous to  the  arrangement  of  foliage  leaves  on  the  branch. 
We  learned  also,  in  our  study  of  inflorescence,  that  flowers 
and  flower  buds  occur  only  in  the  same  positions  where 
leaf  buds  occur,  and  that  they  are  subject  to  the  same  laws 
of  arrangement  and  growth. 

320.  Transformation  of  Organs.  —  In  our  study  of  fruits 
we  saw  that  the  carpels  of  the  ovary  are  merely  trans- 
formed leaves.     We  learned,  also,  in  our  study  of  leaves, 
something  about  the  wonderful  transformations  that  these 
organs  are  capable  of  undergoing ;    and  lastly,  we  have 
found  some  of  these  transformations  taking  place  under 
our  eyes  in  the   leaflike   sepals  and   petal-like   filaments 
of   the   star-of-Bethlehem,   in   the   bracts   of   the   cactus, 
the  scales  of  winter  buds,  and  numerous  other  instances 
recorded  in  the  preceding  pages. 

It  must  not  be  supposed,  however,  that  an  organ  is  ever 
developed  as  one  thing  and  then  deliberately  changed  into 
something  else.  When  we  speak  loosely  of  one  organ 
being  transformed  into  another,  the  meaning  is  merely  that 
it  has  developed  into  one  thing  instead  of  into  something 
else  that  it  was  equally  capable  of  developing  into. 

321.  The  Flower  a  Transformed  Branch.  —  For  the  rea- 
sons mentioned,  the   flower  is  regarded   by  botanists  as 
merely  a  branch  with  transformed  leaves  and  the  inter- 
nodes  indefinitely  shortened  so  as  to  bring  the  successive 
cycles  into  close  contact,  the  whole  being  greatly  altered 
and  specialized  to  serve  a  particular  purpose. 


NATURE  AND   OFFICE   OF  THE   FLOWER          223 

322.  The  Course  of  Floral  Evolution.  — With  this  concep- 
tion of  the  nature  of  the  flower  we  can  readily  see  that  the 
less  specialized  its  organs  are  and  the  more  nearly  they 
approach  in  structure  and  arrangement  to  the  condition  of 
an  undifferentiated  branch,  the  more  primitive  and  unde- 
veloped the  type  to  which  it  belongs.     On  the  other  hand, 
if  the  parts  are  highly  specialized  and  widely  differentiated 
from  the  crude  branch,  a  proportionately  high  stage  of 
floral  evolution  is  indicated. 

323.  Office  of  the  Flower.  — The  one  object  of  the  flower 
is  the  production  of  fruit  and  seed,  and  all  its  wonderful 
specializations  and  variations  of  form  and  color  tend  either 
directly  or  indirectly  to  that  end. 

324.  Fertilization.  —  It  was  stated  in  Section  286  that  no 
seed  can  be  developed  unless  some  of  the  pollen  reaches 
the  stigma,  but  even  this  is  not  sufficient  unless  the  process 
known    as    fertilization    takes    place.     The    exact   nature 
of  this  process  it  is  not  easy  to  explain  without   going 
into  details  beyond  the  scope  of  this  work,  but  a  good 
general  idea  of   fertilization    may  be   obtained   by   refer- 
ring   to    Figure  443    in   connection  with  a  study  of  the 
pollinated  pistil  of  some  large  flower,  like  the  hollyhock 
or  hibiscus. 

325.  The  Pollen  Tubes.  —  Obtain  if  possible  the  flower 
of  a  Syrian  hibiscus  (okra  will  answer  nearly  as  well)  that 
has  begun  to  close  up,  or  to  change  color,  and  compare 
the  stigma  with  that  of  a  freshly  opened  flower.     What  dif- 
ference do  you  observe  in  the  pollen  grains  adherent  to 
each  ?     The  yellow,  withered  look  of  the  former  is  due  to 
the  fact  that  they  have  begun  to  germinate  on  the  moist 
surface  of  the  stigma ;  that  is,  to  send  clown  little  tubes 
into  its  substance  (Fig.  443,  z),  and  the  nourishment  con- 
tained in  the  grain  is  being  used  up,  just  as  the  endosperm 
of  the  seed  is  used  up  when  the  embryo  begins  to  germi- 
nate.     (The  germination  of  pollen,  however,  means  some- 
thing very  different  from  the  germination  of  the  seed,  and 


224 


THE   FLOWER 


must  not  be  confounded  with  it.)     The  pollen  tube  con- 
tinues to  elongate  until  it  passes  down  through  the  base  of 

the    style    into    the    ovary    (Fig. 

443,  m]. 


326.  Course  of  the  Pollen  Tube. 
— The  time  taken  for  the  tube  to 
penetrate  to  the  ovary  varies  in 
different  flowers 
according  to  the 
distance  traversed 
and  the  rate  of 
growth.  In  the 
crocus  it  takes 
from  one  to  three 


443. —  Diagram  of  a  simple 

flower,  showing  course  of  the     d  m   the    spot. 

pollen    tube:     a,     transverse  J  i 

section  of  an  anther  before  its  ted  Calla  \AfTtM 
dehiscence;  b,  an  anther  de-  wiftculcituni}  about 
hiscing  longitudinally,  with 

pollen;  c,  filament;  d,  base  of  five  days,  and  in 
floral  leaves;  e,  nectaries;  / 
wall  of  carpels ;  g,  style ;  h, 
stigma;  i,  germinating  pollen 
grains ;  m,  a  pollen  tube  which 
has  reached  and  entered  the 
micropyle  of  the  ovule;  n, 
funicle  of  ovule;  a,  its  base;  ^  ^^  ^.^  ^  ^^  ^  ^ 

can    not   well   exceed   twenty-four 


orchids,  from  ten 
to  thirty  days.  In 
the  hibiscus  and 
many  others  of 


444.  —  A  pollen 
grain  emitting  a  tube 
(magnified). 


antipodal  cells;  v,  synergidae; 
2,  oosphere. 


/,  outer  integument ;  q,  inner 
integument;  s,  nucellus  of 
ovule ;  /,  cavity  of  the  embryo  n  r  n 

sac;  «,  its  basal  portion  with  hours,  as  the  corolla  usually  falls 
away  on  the  evening  of  the  day  on 
which  it  expanded,  carrying  the 

style  and  stamens  with  it,  so  that  if  the  pollen  tube  had 
not  reached  the  ovary  by  that  time  it  could  never  'get 
there  at  all.  Sometimes  the  pistil  is  hollow,  affording  a 
free  passage  to  the  pollen  tube ;  in  other  cases  it  is  solid 
and  the  growing  tube  eats  its  way  down,  as  it  were,  feed- 
ing upon  the  substance  of  the  pistil  as  it  grows.  How  is 
it  in  the  flower  you  are  examining  ?  In  some  orchids  the 
pollen  tubes  can  be  seen  by  the  unaided  eye,  massed 
together  within  the  thickened  style,  looking  like  a  strand 
of  fine  white  floss.  It  takes  a  grain  of  pollen  to  fertilize 


NATURE   AND   OFFICE   OF   THE   FLOWER          225 

each  ovule,  and  where  more  than  one  seed  is  produced  to 
a  carpel,  as  is  commonly  the  case,  at  least  as  many  pollen 
tubes  must  find  their  way  to  each  cell  of  the  ovary  as 
there  are  ovules  —  provided  all  are  fertilized. 

327.  Formation  of  the  Seed.  —  When  a  pollen  tube  has 
penetrated  to  the  ovary  it  next  enters  one  of  the  ovules, 
usually  through  the  micropyle  (Fig.  443,  m).      There  it 
penetrates  the  wall  of  a  baglike  inclosure  called  the  em- 
bryo sac  (Fig.  443,  u,  t,  z],  where  a  series  of  changes  takes 
place  too  intricate  to  be  described  here,  by  which  a  fusion 
is  brought  about  between  a  portion  of  the  contents  of  cer- 
tain cells  emitted  by  the  pollen  tube  and  a  large  cell  con- 
tained in  the  embryo  sac,  known  as  the  germ  cell,  or  egg 
cell  (Fig.  443,  *.).  |  The  fusion  of  these  two  bodies  is  what 
constitutes  fertilization.  )  The  cell  formed  by  their  union 
finally  develops  into  the  embryo. and  the  other  contents  of 
the  sac  into  the  endosperm,  and  the  ripened  ovules  become 
the  seeds. 

328.  Stability  of  the  Process  of  Fertilization.  —  The  pro- 
cesses of  fertilization  and  reproduction  are  very  obscure 
and  difficult  to  understand  without  a  degree  of  skill  in  the 
manipulation  of  the  microscope  and  a  knowledge  of  tech- 
nical details  that  the  ordinary  observer  can  seldom  acquire. 
The  phenomena  that  characterize  them,  however,  are  the 
most  uniform  and  stable  of  all  the  life  processes,  varying 
little  not  only  in  different  species  and  orders,  but  through- 
out the  whole  vegetable  kingdom.      For  this  reason  they 
furnish  a  more  reliable  standard  for  judging  of  the  real 
affinities  of  plants  than  mere  external  resemblances,  which 
are  more  liable  to  variation  and  may  often  be  accidental, 
and  so  they  have  been  chosen  by  botanists  as  the  ultimate 
basis  for  the  classification  of  plants. 

329.  Embryology.  —  The  study  of  the  developing  ovule, 
known  as  embryology,  is  a  comparatively  recent  branch  of 
science,  and  has  resulted  in  overturning  many  of  the  ideas 
of  the  older  botanists  and  the  abandonment  of  many  of  the 

ANDREWS'S  EOT.  —  I  5 


226  THE   FLOWER 

established  terms,  which  would  now  be  misleading  because 
they  were  founded  upon  false  assumptions.  This  has  led  to 
a  most  unfortunate  confusion  in  botanical  terminology,  the 
compensation  for  which  lies  in  the  hope  that  as  investi- 
gation brings  new  truths  to  light  greater  clearness  and 
certainty  will  grow  out  of  the  temporary  disorder. 

FIELD  WORK 

Look  for  examples  of  transition  from  one  organ  to  another.  These 
are  particularly  apt  to  occur  in  the  so-called  double  flowers  of  the 
garden,  and  in  those  generally  that  have  any  of  their  organs  indefinitely 
multiplied.  Examine  bracts  and  bud  scales  of  different  kinds,  the  car- 
pellary  leaves  of  leaflike  follicles,  such  as  those  of  the  Japan  varnish 
tree,  milkweeds,  columbine,  and  all  sorts  of  vegetable  monstrosities, 
which  will  generally  be  found  to  result  from  transformations  of  some 
sort.  Study  the  numerical  plan  of  some  of  the  commonest  flowers  of 
your  neighborhood ;  note  the  arrangement  and  consolidation  of  their 
organs,  and  determine  their  relative  place  in  the  evolutionary  scale. 

Make  a  list  of  all  the  outdoor  plants,  both  wild  and  cultivated,  that 
are  found  blooming  in  your  neighborhood,  keeping  a  record  of  the 
earliest  specimens  of  each  as  you  find  them.  The  best  way  is  to  keep  a 
sort  of  daily  calendar,  and  at  the  end  of  each  month  give  a  summary  of 
all  the  species  found  in  bloom  during  that  period.  In  this  way  a  fairly 
complete  annual  record  of  the  flowering  time  of  the  different  plants  for 
that  vicinity  will  be  obtained.  The  record  should  be  kept  up  the  whole 
year  round.  Don't  stop  in  winter,  but  go  straight  on  through  the  coldest 
as  well  as  the  hottest  season,  and  you  will  make  some  surprising  dis- 
coveries, especially  if  the  record  is  kept  up  year  after  year.  Give  the 
common  name  of  each  plant,  adding  the  botanical  one  if  you  know  it. 
Any  facts  that  you  may  know  or  may  discover  in  regard  to  particular 
plants,  such  as  their  medicinal  or  other  uses,  their  poisonous  or  edible 
properties,  the  insects  that  visit  them,  and  in  the  case  of  weeds,  their 
origin  and  introduction,  will  greatly  enhance  the  interest  and  value 
of  the  record. 

POLLINATION 

MATERIAL.  —  This  subject  must  be  studied  in  the  field  and  garden  ; 
no  special  directions  for  seeking  material  are  needed. 

330.  Prevention  of  Self-Pollination.  —  The  most  interest- 
ing chapter  in  the  history  of  plant  life  is  that  relating  to 
the  conveyance  of  pollen  from  the  anther  to  the  stigma. 


POLLINATION 


227 


It  was  recognized  by  the  older  botanists  that  this  transfer 
was  necessary  to  the  production  of  fruit,  but  they  were 
puzzled  for  nearly  two  hundred  years  by  the  fact  that 
many  flowers  seem  to  be  constructed  as  if  on  purpose  to 
defeat  this  object.  In  our  examination  of  the  iris,  for 
instance,  it  was  seen  that  the  anthers  lie  under  the  broad 


445  446 

445,  446.— Flower  of  fireweed  (Epilobium  angustifolium)  (GRAY):  445,  with 
mature  stamens  and  immature  pistil ;  446,  the  same  a  few  days  older,  with  expanded 
pistil  after  the  anthers  have  shed  their  pollen. 

divisions  of  the  style  in  such  a  manner  that  the  pollen 
from  them  can  not  possibly  reach  the  stigma  without  ex- 
ternal agency  ;  and  in  all  monoecious  and  dioecious  plants, 
self-pollination  is  clearly  impossible.  In  other  cases,  of 
which  the  cone  flower  {Rudbeckia)  and  the  common  sage 
furnish  examples,  the  anthers  and  stigma  in  the  same 
flower  do  not  mature  together,  thus  producing  the  same 
effect  as  if  they  were  unisexual. 

331.  Dimorphism  is  an  expression  for  denoting  a  con- 
dition in  which  the  stamens  and  pistils  are  of  different 
relative  lengths  in  different 
flowers  of  the  same  species, 
the  stamens  being  long  and 
the  pistils  short  in  some,  the 
pistils  long  and  the  stamens 
short  in  others.  Flowers  of 
this  sort  are  said  to  be  dimor- 
phous, or  dimorphic,  that  is, 
of  two  forms ;  and  some 
species  are  even  trimorphic,  having  the  two  sets  of  organs 
long,  short,  and  medium,  respectively,  in  different  indi- 


447  44<* 

447,  448.  — Flower  of  pulmonaria: 
447,  long  styled  ;  448,  short  styled. 


228 


THE   FLOWER 


viduals.      Examples  of  dimorphic  flowers  are  the  pretty 

little  bluets  (Honsfonia  ccerulea),  the  partridge  berry  (  Mit- 

chella  repens},  the  swamp  loosestrife  (Lythrum  lineare}, 

and  the  English 
cowslip.  Of  tri- 
morphic  flowers 
we  have  exam- 
ples in  the  wood 
sorrel,  and  the 
spiked  loosestrife 
(Lythrum  salica- 
ria)  of  the  gar- 
dens. These 
flowers  were  a 
great  puzzle  to 

botanists  until  the  celebrated  naturalist,  Charles  Darwin, 

proved  by  a  series  of  careful  experiments  that  the  seed  pro- 

duced by  pollinating  a  dimorphous  flower  with  its  own  pollen, 

or   with   pollen    from    a 

flower  of  similar  form,  are 

of  very  inferior  quality  to 

those   produced    by   im- 

pregnating a  long-styled 

flower  with  pollen  from 

a   short-styled   one,  and 

vice  versa. 


449-451.  —  Three  forms  of  Lythrum  salicaria. 


332.  Wind  Pollination. 
—  But  the  problem  is 
only  half  solved  when  a 
plant  has  been  rendered 
incapable  of  impreg- 
nating itself.  Cross- 
pollination,  that  is,  the 
transfer  of  pollen  from  a 
separate  flower  or  plant, 
has  been  rendered  necessary,  and  provision  must  now  be 
made  for  the  transportation.  In  many  cases,  of  which  the 


452.  —  Feathery  stigmas  of  a  grass  adapted 
to  wind  pollination. 


POLLINATION  229 

pine,  Indian  corn,  oaks,  ragweed,  and  grasses  of  all  sorts 
afford  abundant  examples,  this  is  accomplished  by  the 
wind.  This  is  a  very  clumsy  and  wasteful  method,  how- 
ever, for  so  much  pollen  is  lost  by  the  haphazard  mode  of 
distribution  that  the  plant  is  forced  to  spend  its  energies 
in  producing  a  vast  amount  more  than  is  actually  needed, 
and  great  masses  of  it  are  frequently  seen  in  spring  floating 
like  patches  of  sulphur  on  ponds  and  streams  in  the 
neighborhood  of  pine  thickets.  Wind-pollinated  flowers 
are  called  by  botanists  anemophilous,  a  word  meaning 
"wind-loving."  Like  those  that  are  self -pollinated,  they 
are  generally  very  inconspicuous,  devoid  of  odor  and  of 
all  attractions  of  form  or  color,  b'ecause  they  have  no 
need  of  these  allurements  to  attract  the  visits  of  insects. 

333.  Insect  Pollination.  —  A  more   economical   method 
of  securing  pollination  is  through  the  agency  of  insects. 
In  probing  around  for  the  nectar  or  the  pollen  upon  which 
they  feed,  these  busy  little  creatures  get  themselves  dusted 
with  the  fertilizing  powder,  which  they  unconsciously  con- 
vey from  the  stamen  of  one  flower  to  the  pistil  of  another. 
Insects  usually  confine  themselves,  as  far  as  possible,  to 
the  same  species  during  their  day's  work,  and  since  less 
pollen  is  wasted  in  this  way  than  would  be  done  by  the 
wind,  it  is1  clearly  to  the  advantage  of  a  plant  to  attract 
such  visitors,  even   at  the  expense  of   a  little  honey,  or 
of  a  liberal  toll  out  of  the  pollen  they  distribute. 

Flowers  that  have  adapted  themselves  to  insect  polli- 
nation are  said  to  be  entomophilous,  insect  lovers,  and  all 
their  various  attractions  of  form,  color,  and  odor  have  been 
developed,  not  for  the  gratification  of  man,  as  human 
arrogance  and  self-conceit  have  so  long  asserted,  but  as 
notifications  to  their  insect  guests  that  the  banquet  of 
nectar  is  spread. 

334.  Special  Partnerships.  —  Some  plants  have  adapted 
themselves  to  the  visits  of  one  particular  kind  of  insect 
so  completely  that  they  would  die  out  if  that  species  were 
to  become  extinct.     The  well-known  alliance  between  red 


230 


THE   FLOWER 


clover  and  the  bumblebee  was  brought  to  light  a  few 
years  ago  when  the  plant  was  first  introduced  into  Aus- 
tralia. It  grew  luxuriantly  and  blossomed 
profusely,  but  would  never  set  seed  till  the 
bumblebee  was  introduced  to  keep  it  com- 
pany. 

The  most  remarkable  of  these  partnerships, 
perhaps,  yet  observed  by  naturalists,  is  that 
which  exists  between  the  little  pronuba,  or 
yucca  moth,  and  the  flowering  yuccas,  of 
which  the  bear's  grass  and  Spanish  bay- 
453. -Pod  of  onet  of  our 


yucca     angustl 


fields  and 


folia  pierced  by  . 

the    Pronuba   roadsides  are 


familiar  ex- 
amples. If  any  of  these 
plants  grow  in  your  neigh- 
borhood, examine  the  pods 
and  observe  that  none  of 
them  are  perfect,  but  all 

.     .  454.  —  Moth  resting  on  yucca  blossom. 

show  a  constriction  at  or 

near  the  middle,  such  as  is  sometimes  seen  in  the  sides 
of  wormy  plums  and  pears.  This  is  caused 
by  the  larvae  of  the  moth,  which,  feed  upon 
the  unripe  seeds.  If  you  will  look  under 
the  nodding  perianth  of  a  yucca  blossom 
(Fig.  454),  you  will  see  that  the  short  sta- 
mens are  curved  back  from  the  pistil  in 
such  a  manner  that  under  ordinary  circum- 
stances, not  a  grain  of  the  pollen  can  fall 
upon  it  except  by  the  rarest  accident.  But 
the  yucca  moth  is  a  good  farmer  as  well 
as  a  provident  mother,  and  as  soon  as  she 
455.—  Pronuba  has  deposited  her  eggs  in  the  seed  vessel, 
takes  care  to  provide  a  crop  of  food  for  her 
offspring  by  gathering  a  ball  of  pollen  in 

her  antennae  and  deliberately  plastering  it  over  the  stigma 

(Fig.  455).     In  this  way  she  insures  the  perfecting  of  the 


pollinating  pistil 

of  yucca. 


POLLINATION  231 

fruit  and  the  proper  nourishment  of  her  children.  When 
the  eggs  are  hatched  the  larvae  feed  upon  the  unripe 
seeds  for  a  time,  but  it  is  rare  that  more  than  a  dozen  or 
two  are  destroyed  in  a  pod,  so  that,  after  all,  the  plant 
pays  only  a  moderate  commission  for  the  service  rendered. 
An  equally  interesting  partnership  exists  between  the 
Smyrna  fig  and  the  little  insect,  Blastophaga,  an  account 
of  which  may  be  found  in  the  Year  Book  of  the  Depart- 
ment of  Agriculture  for  1900.  In  these  cases  the  mutual 
dependence  is  so  complete  that  neither  the  plant  nor  the 
animal  could  exist  without  the  other. 

335.  Protective  Adaptations.  —  Where  plants  have 
adapted  themselves  to  insect  pollination  it  is,  of  course, 
important  to  shut  out  intruders  that  would  not  make  good 
carriers.  In  general,  small,  creeping  things  like  ants  and 
plant  lice  are  not  so  efficient  pollen  bearers  as  winged 
insects,  and  hence  the  various  devices,  such  as  hairs,  sticky 
glands,  scales,  and  constrictions  at  the  throat  of  the  corolla, 
by  means  of  which  their  access  to  the  pollen  is  prohibited. 
To  this  class  of  adaptations  belong  the  hairy  filaments  of 
the  spiderwort,  the  sticky  ring  about  the  peduncles  of 
the  catchfly,  the  swollen  lips  of  the  snapdragon,  the  scales 
or  hairs  in  the  throat  of  the  hound's-tongue,  the  velvet 
petals  of  the  par- 
tridge berry,  etc. 

Of  flowers  that 
are  pollinated  by 
night  moths,  some 
close  during  the  day, 
as  the  four-o'clock 
and  the  evening 

primrose;     and     vice          456,  457.—  Protection  of  pollen   in  the  thistle: 


versa,  the  morning.  '"  ""  """""  '  ™'  »* 

glory,  dandelion,  and 

day  flower  (Commelyna),  unfold  their  beauties  only  to 
the  sun.  For  similar  reasons,  night-blooming  flowers  are 
generally  white  or  very  light  colored,  and  shed  their  fra- 


232 


THE   FLOWER 


grance  only  after  sunset.  A  nodding  position  is  assumed 
by  many  flowers  at  night  or  during  a  shower  to  keep  the 
pollen  from  being  inj  ured  by  rain  and  dew. 


458  459 

458,  459.  — A  bell  flower:  458,  position  in  daylight;  459,  position  at  night, 
or  during  wet  weather. 

336.  Fraud  and  Robbery.  —  The  secretion  of  honey  by 
flowers  is  a  very  common  means  of  attracting  insect  visit- 
ors. In  general,  plants  that  have  very  long, 
tubular  corollas,  like  the  trumpet  honeysuckle 
(Lonicera  sempervirens],  and  trumpet  vine, 
are  reserving  their  sweets  for  humming  birds 
and  long-tongued  moths  and  butterflies. 
Acleisanthes,  a  plant  of  the  four-o'clock 
family  that  grows  along  our  Mexican  border 
(Fig.  460),  has  a  tube  from  twelve  to  four- 
teen centimeters  long  (about  five  and  one 
half  inches).  Yet  even  deeper  corollas  than 
this  can  be  explored  by  a  humming  bird  of 
South  America,  which  has  a  bill  that  some- 
times reaches  the  length  of  fifteen  centi- 
4oo.-Tubu-  meters  (about  six  inches),  and  a  tongue  that 
lar  blossom  of  can  be  protruded  nearly  as  far  again  (Fig. 

Acleisanthes  l  ° 

4oi).     It  is  not  uncommon,  however,  to  find 


POLLINATION  233 

such  corollas  with  a  hole  in  the  tube  near  the  base,  made 
by  thieving  bees  and  wasps  which  thus  get  at  the  honey 
surreptitiously,  without 
paying  their  tribute  of 
pollen.  On  the  other 
hand,  plants  like  the  car- 
rion flower,  and  skunk  461- Head  and  bill  of  sword  bird 

(Doctmastes  ensiferus). 

cabbage  seem  to  practice 

a  kind  of  fraud  upon  flesh  flies  by  imitating  the  colors 

and  odors  of  the  garbage  upon  which  such  creatures  feed. 

337.  Experiments.  —  An  instructive  experiment  may  be 
made  with  regard  to  the  color  preferences  of  insects  by 
putting  a  drop  or  two  of  syrup  on  bits  of  glass  and  laying 
them  on  paper  of  different  colors  in  the  neighborhood  of 
a  beehive  or  other  place  frequented  by  insects,  and  ob- 
serving which  color  seems  to  attract  them  most.     Similar 
experiments  may  be  made  with  perfumes  and  flavorings. 

338.  Color,  being  a  very  variable  and  unstable  quality,  is 
of  little  use  in  classifying  flowers,  yet  it  is  interesting  to 
know  that  all  their  endless  variations  of  hue  are  confined 
approximately  within  certain  limits.    Nobody  has  ever  seen 
a  blue  rose  or  a  yellow  aster,  and  though  the  florist's  art 
is  constantly  narrowing  the  application  of  this  law,  it  still 
remains  true  that  in  a  state  of  nature  certain  colors  seem 
to  be  associated  together  in  the  floral  art  gamut.     Yellow 
is  considered  by  botanists  the  simplest  and  most  primitive 
color   in   flowers,  and   blue   the   latest   and    most   highly 
evolved.     Yellow,  white,  and  purple,  in  the  order  named, 
are  the  commonest  flower  colors  in  nature ;  blue  the  rarest. 

PRACTICAL  QUESTIONS 

1.  Why  do  the   flowers   of  oak,  willow,  and   other  wind-fertilized 
plants  generally  appear  before  the  leaves?     (332.) 

2.  Can    you  account    for    the   "showers    of   sulphur"   frequently 
reported  in  the  newspapers?     (332.) 

3.  Do   you   see   any  connection   between  the   feathery  stigmas  of 
most  grasses  and  their  mode  of  pollination?     (332.) 


234 


THE   FLOWER 


4.  Why  are  wind-fertilized  plants  generally  trees  or  tall  herbs? 

5.  If  March   winds   should  cease  to  blow,   would  vegetation  be 
affected  in  any  way? 

6.  Can  you  trace  any  connection  between  the  winds  and  the  corn 
crop? 

7.  Is  it  good  husbandry  to  plant  different  varieties  of  corn,  or  other 
grain  in  the  same  field? 

8.  Why  do   the  seeds  of  fruit  trees  so  seldom  produce  offspring 
true  to  the  stock?     (333.) 

9.  Would  you   place  a  beehive   near  a  field  of  buckwheat?    Of 
clover?     Near  a  strawberry   bed?     In  a  peach  orchard?     Near  a  fig 
tree  ?     Under  a  grape  arbor  ? 

10.  Why  are  very  conspicuous  flowers  like  the  camellia,  hollyhock, 
and  pelargoniums  so  frequently  without  odor? 

11.  Why  is  the  wallflower  -'sweetest  by  night"?    (335.) 

12.  What  advantage  can  flowers  like  the  morning-glory  gain  by  their 
early  closing?     (335.) 

13.  Of  what  use  to  the  cotton  plant,  Japan  honeysuckle,  and  hibis- 
cus is  the  change  of  color  their  blossoms  undergo  a  few  hours  after 
opening?    (335.) 

14.  Why  does  the  Japan  honeysuckle,  that  has  run  wild  so  abun- 
dantly in  many  parts  of  our  country,  produce  so  few  berries? 

15.  If  the   trumpet  vine  grows  in  your  neighborhood,   examine  a 
number  of  corollas  and  account  for  the  dead  ants  found  in  them.     Try 
to  account  also  for  the  large  hole  (sometimes  three  quarters  of  an  inch 
in  diameter)  often  found  near  the  base  of  the  tube.     (336.) 

1 6.  Do  you  see  any  connection  between  the  greater  freshness  and 
beauty  of  flowers  early  in  the  morning  and  the  activity  of  bees,  birds, 
and  butterflies  at  that  time  ? 

17.  The  flowers  most  frequented  by  humming  birds  are  the  trumpet 
honeysuckle,  cardinal  flower,   trumpet  vine,  horse  mint    (Monarda), 
wild  columbine,  canna,  fuschia,  etc. ;  what  inference  would  you  draw 
from  this  as  to  their  color  preferences  ? 


FIELD  WORK 

The  subject  is  itself  so  suggestive  that  it  is  hardly  necessary  to  do 
more  here  than  append  a  list  of  some  of  the  plants  which  it  would  be 
interesting  to  examine  with  reference  to  their  mode  of  pollination. 

The  orchids  present  the  most  wonderful  adaptations  for  insect  polli- 
nation, of  all  the  vegetable  kingdom,  but  they  are  rare  and  difficult  to 
be  obtained,  so  it  is  better  to  look  for  specimens  nearer  home.  In 
neighborhoods  where  the  pogonia,  the  purple  and  yellow  fringed  orchis, 
or  the  moccasin  flower  (Cypripedium)  are  found,  they  should,  of 
course,  receive  attention.  Some  more  easily  obtainable  specimens  are : 


POLLINATION 


235 


Wallflower 

Bouncing  Bet     . 

Columbine 

Monkshood 

Larkspur    . 

Barberry     . 

Mignonette 

Pansy 

Syrian  Hibiscus 

Cotton        .  „      . 

Nasturtium         .        . 

Touch-me-not    . 

Wood  sorrel 

Horse-chestnut  . 

Buckeye     . 

Pea    . 

Bean  .... 

Ground  nut 

Vetch 

Wistaria     . 

Black  locust 

Clover 

Apple,  pear 

Peach 

Loosestrife 

Maypop 

Gourds,  squashes,  etc. 

Trumpet  honeysuckle 

Japan  honeysuckle 

Partridge  berry  . 

Cone  flower 

Dandelion 

Ox-eye  daisy 

Bell  flower 

Mountain  laurel 

Andromeda 

Primrose    . 

Persimmon 

Lilac. 

Periwinkle 

Milkweed  . 

Snapdragon 

Lousewort 

Trumpet  vine     . 

Horse  balm 


Cheiranthus  cheiri. 

Saponaria  officinalis. 

Aquilegia  vulgaris. 

Aconitum  napellus. 

Delphinium  (various  species). 

Berberis  vulgaris. 

Reseda  odorata. 

Viola  tricolor. 

H.  syriacus. 

Gossypium  (various  kinds). 

Tropaeolum  majus. 

Impatiens  (various  species). 

Oxalis  (various  species) 

^Csculus  hippocastanum. 

yEsculus  pavia,  flava,  parviflora. 

Pisum  (various  species). 

Phaseolus  (various  species). 

Apios  tuberosa. 

Vicia. 

Wistaria. 

Robinia  pseudacacia. 

Trifolium  (various  species). 

Pyrus. 

Prunus  persica. 

Lythrum  salicaria. 

Passiflora  incarnata. 

Cucurbitaceae  (various  kinds). 

Lonicera  sempervirens. 

Lonicera  Japonica. 

Mitchella  repens. 

Rudbeckia. 

Taraxacum  oflkinafe. 

Chrysanthemum  leucanthemum. 

Campanula  rapunculoides. 

Kalmia  latifolia. 

A.  ligustrina. 

Primula  officinalis,  P.  grandiflora 

Diospyros  virginiana. 

Syringa  vulgaris. 

Vinca  major,  V.  minor. 

Asclepias  (various  species). 

Antirrhinum  majus. 

Pedicularis  canadensis. 

Tecoma  radicans. 

Collinsonia  canadensis. 


236  THE   FLOWER 

Dead  nettle        ....  Lamium  amplexicaule,  L.  album. 

Sage.         .      '   ;         .         .         •  Salvia  officinalis  and  other  species. 

Catmint      .....  Nepeta  cataria. 

Iris •  Iris  (various  kinds). 

Carrion  flower    ....  Smilax  herbacea. 

Bear's  grass        .         .         .  Yucca  filamentosa. 

Spanish  bayonet         .         .         .  Yucca  aloifolia. 

Lily  of  the  valley        .         .         .  Convallaria  majalis. 

Day  lily Hemerocallis  fulva. 

PRACTICAL  EXPERIMENTS 

Experiments  should  be  made  by  enveloping  buds  of  various  kinds  in 
gauze,  so  as  to  exclude  the  visits  of  insects,  and  noting  the  effect  upon  the 
production  of  fruit  and  seed.  Envelop  a  cluster  of  milkweed  blossoms 
in  this  way  and  notice  how  much  longer  the  flowers  so  protected  con- 
tinue in  bloom  than  the  others;  why  is  this?  Try  the  same  experi- 
ment upon  the  blooms  of  cotton  and  hibiscus  if  you  live  where  they 
grow,  and  see  whether  the  characteristic  change  in  color  occurs  in 
flowers  from  which  insects  have  been  excluded  and  whether  good  seed 
pods  are  produced  by  them.  Try  the  effect  upon  fruit  production  of 
excluding  insects  from  clusters  of  apple,  pear,  and  peach  blossoms. 


IX.     ECOLOGY 

ECOLOGICAL  FACTORS 

339.  Definition.  —  By  ecology  is  meant  the  relations  of 
plants  to  their  surroundings.     These  may  be  classed  under 
three  general  heads:  their  relations  to  inanimate  nature, 
to  other  plants,  and  to  animals.      The  subject  has  been 
touched  upon  repeatedly  in  the  foregoing  pages,  and,  in 
fact,  it  is  impossible  to  treat  of  any  branch  of  botany  with- 
out some  reference  to  it.     All  that  was  said  about  the  ad- 
justment of  leaves  for  light  and  moisture,  and  their  adap- 
tations for  protection   and  food   storage,  the  devices  for 
fruit   and   seed    dispersal,  etc.,  really  belong  to  ecology, 
while  Sections  330-338,  about  pollination,  may  be  regarded 
as  a  very  imperfect  review  of  the  ecology  of  the  flower  in 
relation  to  the  insect  world. 

340.  Symbiosis.  —  Associations   for   mutual   help,    like 
those  described  in  Sections  330-338,  between  certain  plants 
and  their  insect  visitants,  have  been  included  by  botanists 
under  the  general  term,  symbiosis,  a  word  which  means 
"living  together."     In  its  broadest  sense  symbiosis  refers 
to    any  sort   of   dependence  or  intimate  organic  relation 
between  different  kinds  of  individuals,  and  so  may  include 
the  climbing  and  parasitic  habits ;  but  it  is  more  properly 
restricted  to  cases  where  the  relation  is  one  of  mutual 
benefit.     It  may  exist  either  between  plants  of  one  kind 
with  another,  between  animals  with  animals,  or  between 
plants  and  animals,  as  in  the  case  of  the  clover  and  bumble- 
bee, and  the  yucca  and  pronuba. 

The  occurrence  of  the  root  tubercles  on  certain  of  the 
leguminosae  (Sec.   198)  is  a  clear  case  of  symbiosis,  the 
microscopic  organisms  in  the  tubercles  getting  their  food 
237 


238  ECOLOGY 

from  the  plant  and  at  the  same  time  enabling  it  to  get 
food  for  itself  from  the  air  in  a  way  that  it  could  not 
otherwise  do. 

341.  Relations  with  Inanimate  Nature.  —  But  it  is  to  the 

relations  of  plants  with  inanimate  nature,  and  their  group- 
ing into  societies  under  the  influence  of  such  conditions, 
that  the  term  "ecology"  is  more  strictly  applied.  The  ex- 
ternal conditions  that  lead  to  the  grouping  are  called 
ecological  factors.  The  most  important  of  these  are  tem- 
perature, moisture,  soil,  light,  and  air,  including  the  direc- 
tion and  character  of  the  prevailing  winds.  Each  of  these 
factors  is  complicated  with  the  others  and  with  conditions 
of  its  own  in  a  way  that  often  makes  it  difficult  to  determine 
just  what  effect  any  one  of  them  may  have  in  the  formation 
of  a  given  plant  society. 

342.  Temperature,  for  instance,  may  be  even  and  steady 
like  that  of  most  oceanic  regions,  or  it  may  be  subject  to 
sudden  caprices  and  variations  like  the  "  heated  terms " 
and  "cold  snaps"  that  afflict  our  northern  and  southern 
States  respectively  every  few  years.     We  must  remember, 
too,  that  it  is  not  the  average  temperature  of  a  climate  but 
its  extremes,  especially  of  cold,  that  limit  the  character  of 
vegetation. 

Temperature  probably  has  more  influence  than  any  other 
factor  in  the  distribution  of  plants  over  the  globe,  but  it 
can  have  little  or  no  effect  in  evolving  local  differences  in 
vegetation  because  the  temperature  of  any  given  locality, 
except  on  the  sides  of  high  mountains,  will  ordinarily  be 
practically  the  same  within  a  circuit  of  many  miles. 

343.  Moisture,  again,  may  be  of  all  degrees,  from  the 
superabundance  of  lakes  and  rivers  and  standing  swamps, 
to  the  arid  dryness  of  the  desert,  and  the  water  may  be 
still  and  sluggish,  or  in  rapid  motion.     It  may  exist  more 
or  less  permanently  in  the  atmosphere,  as  in  moist  climates 
like  those  of    England  and   Ireland,  where  vegetation  is 
characterized  by  great  verdure,  or  it  may  come  irregularly 


ECOLOGICAL   FACTORS 


239 


in  the  form  of  sudden  floods,  or  at  fixed  intervals,  causing 
an  alternation  of  wet  and  dry  seasons.  Moreover,  the 
moisture  of  the  soil  or  the  atmosphere  may  be  impregnated 
with  minerals  or  gases  which  may  affect  the  vegetation 
independently  of  the  actual  amount  of  water  absorbed. 

344.  Light  may  be  of  all  degrees  of  intensity,  from  the 
blazing  sun  of  the  treeless  plain  to  the  darkness  of  caves 
and  cellars  where  nothing  but  mold  and  slime  can  exist. 
Between  these  extremes  are  numberless  intermediate  stages ; 
the  dark  ravines  on  the  northern  side  of  mountains ;  the 
dense  shade  of  beech  and  hemlock  forests  ;  the  light,  lacy 
shadows  of  the  pines;  each  characterized  by  its  peculiar 
form  of  vegetation.     Absence  of  light,  too,  is  usually  ac- 
companied by  a  lowering  of  temperature  and  reduction  of 
transpiration,  factors  which  tend  to  accentuate  the  differ- 
ence between  sun  plants  and  shade  plants,  giving  to  the 
latter  some  of   the  characteristics  of   aquatic  vegetation. 
Generally,  the  tissues  of  these  are  thin  and  delicate,  and 
having  no  need  to  guard  against  excessive  transpiration 
they  wither  rapidly  when  broken. 

345.  Winds  affect  vegetation  not  only 
as  to  the  manner   of    seed   distribution, 
as    in    the    case    of    tumbleweeds    and 

winged  fruits, 
but  directly  by 
increasing  tran- 
spiration, and 
necessitating 
the  develop- 
ment of  strong 
holdfasts  in 

^^Sg^jg"  Plants  growing 
upon  mountain 

sides    and    in    other   exposed    situations. 

The  nature  of  the  region  from  which  they  blow  —  whether 

moist,  dry,  hot,  cold,    etc.,    is   also   an   important   factor. 

In  a  district  open  to  sea  breezes,  live  oaks,  which  require 


462.  —  A  red  cedar 
grown  under  normal 
conditions. 


240 


ECOLOGY 


a  salt  atmosphere,  may  sometimes  be  found  as  far  as  a 
hundred  miles  from  the  coast. 

346.  Soil  is  perhaps  the  most  interesting  of  these  fac- 
tors to  the  farmer,  because  it  is  the  one  that  he  has  it  most 
largely  in  his  power  to  modify.     It  is  to  be  viewed  under 
two  aspects :  first,  as  to  its  mechanical  properties,  whether 
soft,  hard,  compact,  porous,  light,  heavy,  etc. ;  secondly, 
as  to  its  chemical  composition  and  the  amount  of  plant 
food  contained  in  it.     The  first  can  be  regulated  by  tillage 
and  drainage,  the  second  by  a  proper  use  of  fertilizers. 

Under  mechanical  structure  is  included  also  the  power 
of  absorbing  and  retaining  water.  A  good  absorbent  soil, 
i.e.  sand,  or  gravel,  is  not  apt  to  be  a  good  retainer,  while 
clay  and  marl,  that  absorb  slowly,  retain  well. 

347.  Experiment.  —  Take  a  few  handfuls  of  each  of  the 
different  kinds  of  soil  in  your  neighborhood,  free  them  as 
thoroughly  as  possible  from  all  traces  of  vegetation,  place 
separately  in  small  earthen  pots  or  saucers  and  keep  them 
well  moistened.     Pull  up  the  seedling  plants  that  appear 
in  each,  and  keep  a  list  of  them  as  long  as  any  continue  to 
come  up.     What  inference  would  you  draw  from  the  num- 
ber produced  in  each  pot  as  to  the  productiveness  of  the 
different  soils  ?     Could  all  the  seedlings  have  lived  if  they 
had  been  left  to  grow  where  they  came  up  ?     What  be- 
comes of  the  majority  of  seedlings  that  germinate  in  a  state 
of  nature  ? 

PRACTICAL  QUESTIONS 

1.  Is  the  relation  between  man  and  the  plants  cultivated  by  him  a 
symbiosis  ? 

2.  Why  is  it  that  plants  of  the  same,  or  closely  related  species,  are 
found  in  such  different  localities  as  the  shores  of  Lake  Superior,  the  top 
of  Mt.  Washington,  and  the  Black  Mountains  in  North  Carolina?  (342.) 

3.  Which  of  the  five  ecological  factors  described  in  Sections  341-346 
has  probably  influenced  their  distribution?     (342.) 

4.  What  is  the  prevailing  character  of  the  soil  in  your  neighborhood  ? 

5.  Is  your  climate  moist  or  dry?     Warm  or  cold? 

6.  Can  you  trace  any  connection  between  these  factors  and  the  pre- 
vailing types  of  vegetation? 


PLANT   SOCIETIES  241 

PLANT  SOCIETIES 

MATERIAL.  —  A  specimen  of  pipewort  {Eriocaulori),  Sagittaria, 
pondweed,  or  other  succulent  water  plant,  and  a  cactus  of  some  kind. 
The  common  prickly  pear  (Opuntia)  is  the  one  used  in  the  text. 
City  schools  should  have  a  small  aquarium ;  a  few  water  plants  can  be 
kept  in  jars. 

348.  Principles  of  Subdivision.  —  Plants  group  them- 
selves into  societies  not  according  to  their  botanical  rela- 
tionships, but  with  regard  to  the  predominance  of  one  or 
more  of  the  ecological  factors  that  influence  their  growth. 
Sometimes  one  or  two  species  will  take  practical  posses- 
sion of  large  areas,  like  the  coarse  grasses  that  spread 
over  certain  salt  marshes,  or  the  pines  that  formerly  con- 
stituted the  sole  forest  growth  over  extensive  regions  in 
North  Carolina  and  Maine.  But  more  usually  we  shall 
find  a  great  diversity  of  forms  brought  together  by  their 
common  requirements  as  to  shade,  soil,  moisture,  etc. 
These  societies  are,  of  course,  purely  artificial,  and  any 
of  the  factors  named  in  Sections  341-346,  or  others  of  a 
different  kind,  may  be  made  the  basis  of  their  classifica- 
tion. They  might  be  grouped,  for  instance,  according  to 
the  soil  in  which  they  grow,  or  according  to  origin,  whether 
cultivated,  wild,  native,  introduced,  etc.,  as  best  suited  the 
purpose  of  the  classification  in  each  case.  The  moisture 
factor,  however,  has  been  generally  agreed  upon  by  bot- 
anists as  the  one  most  convenient  for  ordinary  purposes. 
Upon  this  principle  plants  are  divided  into  three  great 
groups  :  — 

Hydrophytes,  or  water  plants,  those  that  require  abun- 
dant moisture. 

Xerophytes,  or  drought  plants,  those  that  have  adapted 
themselves  to  desert  or  arid  conditions. 

Mesophytes,  plants  that  live  in  conditions  intermediate 
between  excessive  drought  and  excessive  moisture.  To 
this  class  belong  most  of  our  ordinary  cultivated  plants 
and  the  greater  part  of  the  vegetation  of  the  globe. 

ANDREWS' S  EOT. —  1 6 


242 


ECOLOGY 


Halophytes,  "salt  plants,"  is  a  term  used  to  designate  a 
fourth  class,  based  not  directly  upon  the  water  factor,  but 
upon  the  presence  of  a  particular  mineral  in  the  water  or 
the  soil,  which  they  can  tolerate.  They  seem  to  bear  a 
sort  of  double  relation  to  hydrophytes  on  the  one  hand  and 
to  xerophytes  on  the  other. 

349.  Hydrophyte  Societies.  —  These  embrace  a  number 
of  forms,  from  those  inhabiting  swamps  and  wet  moors  to 
the  submerged  vegetation  of  lakes  and  rivers.  An  exami- 


464.  —  A  hydrophyte  society  of  floating  pond-  465.  —  A  water  plant  (Sagit- 

weed.  taria     natans),     showing     the 

slender,  ribbonlike,  submerged 

nation  01  almost  any  kind  Of  Water      leaves,    the    broad,     rounded, 

plant  will  show  some  of  the  phy-    floa;ing  ones'  and   the  very 

.  r    J         slightly  developed  root  system. 

siological     effects     of     unlimited 

moisture.  Take  a  piece  of  pondweed,  or  other  immersed 
plant  out  of  the  water  and  notice  how  completely  it  col- 
lapses. This  is  because,  being  buoyed  up  by  the  water, 
it  has  no  need  to  spend  its  energies  in  developing  woody 
tissue.  Floating  and  swimming  plants  will  generally  be 
found  to  have  no  root  system,  or  only  very  small  ones, 


PLANT   SOCIETIES 


243 


because  they  absorb  their  nourishment  through  all  parts 

of  the  epidermis  directly  from  the  medium  in  which  they 

live.      That   they   may   absorb 

readily,  the  tissues  are  apt  to 

be  soft  and  succulent  and  the 

walls   of   the   cells    composing 

them  very  thin.      In   some  of 

the  pipeworts  (Eriocaulons) ,  the 

cells    are    so    large    as    to    be 

easily   seen  with    the    unaided 

eye.      If   you   can   obtain   one 

of  these,  examine  it  with  a  lens        466.  —  Transverse  section  through 

and  notice   how  very  thin  the    *«  f m  ,of  a  W™Pp*  P'f 

J  (Elatine  alsmastrum),  showing  the 

Walls    are.        Water    plants    also     very  large  air   cavities  (GOODALE, 

contain    numerous  air  cavities,    afler  REINKE)- 

and  often  develop  bladders  and  floats,  as  in  the  common 

bladderwort,  and  many  seaweeds  (Fig.  467). 

Swamp    plants,    drawing   their    nourishment   from   tbe 

loose  soil  in  which  they  are  anchored,  and  lacking  the 
support  of  a  liquid  medium,  develop 
roots  and  vascular  stems.  The  roots 


467.  —  Seaweed  (sar- 
gassuni)  with  bladderlike 
floats. 


468.  — A  cypress  trunk,  showing  enlarged  base  for 
aeration. 


of  plants  growing  in  swamps  have  difficulty  in  obtaining 
proper  aeration  on  account  of  the  water,  which  shuts  off 
the  air  from  them,  hence  they  are  furnished  with  large 


244 


ECOLOGY 


air  cavities,  and  the  bases  of  the  stems  are  often  greatly 
enlarged,  as  in  the  Ogeechee  lime  (Nyssa  capitata)  and 
cypress,  to  give  room  for  the  formation  of  air  passages. 
The  peculiar  hollow  projections  known  as  "cypress  knees  " 
are  arrangements  for  aerating  the  roots  of  these  trees. 

350.  Xerophyte  Societies  are  adapted  to  conditions  the 
reverse  of  those  affected  by  hydrophytes.  The  extreme 
of  these  conditions  is  presented  by  regions  of  perennial 
drought  like  our  western  arid  plains  and  the  great  deserts 
of  the  interior  of  Asia  and  Africa.  Under  these  conditions 


Switch  plants  "  of  the  alkali  desert,  condensed  into  mere  green  skeletons 
of  vegetation,  and  thus  adapted  to  extreme  xerophyte  conditions. 


plants  have  two  problems  to  solve ;  to  collect  all  the  mois- 
ture they  can  and  to  keep  it  as  long  as  they  can.  Hence, 
plants  of  such  regions  diminish  their  evaporating  surface 
by  reducing  or  getting  rid  of  their  foliage  and  compacting 
all  their  tissues  into  the  stem,  like  the  cactus  (Sec.  209), 
or  they  compress  their  leaves  into  thick  and  fleshy  forms 
fitted  to  resist  evaporation  and  retain  large  amounts  of 
moisture,  as  in  the  case  of  the  yucca  and  century  plant. 
They  also  frequently  develop  a  thick,  hard  epidermis,  or 
cover  themselves  with  protective  hairs  and  scales. 

351.  Examination  of  a  Xerophytic  Plant.  —  Examine  a 
joint  of  the  common  prickly  pear  (Ofuntia),  if  it  grows  in 
your  neighborhood,  or  use  a  potted  cactus,  and  give  your 
reasons  for  regarding  it  as  a  stem  and  not  as  a  leaf. 


PLANT   SOCIETIES  245 

Notice  how  the  spines  are  arranged  on  the  surface,  and 
if  there  are  any  fruits,  buds,  or  flowers,  where  they  occur. 
Peel  off  a  little  of  the  epidermis  and  observe  its  thick, 
horny  texture.  Cut  a  cross  section  through  a  joint  about 
midway  from  base  to  apex  and 
examine  with  a  lens.  Notice  the 
thick  layer  of  green  tissue  next 
the  epidermis,  and  within  that,  a 
band  of  tough,  woody  fibers  in- 
closing the  soft  pulpy  mass  that 
makes  up  the  interior.  (If  the 
woody  layer  is  not  easily  made 
out,  allow  your  specimen  to  dry  ^"-^BliHff 

for  about  twenty-four  hours,  and  it  '//  ^V^V'X 

will  become  quite  distinct.)    Make  JSl 

a  longitudinal  section  through  the  ^yJC 

center  of    a  joint   and  trace  the        470._A  plant  of  opuntia, 

Course     of    the    WOody    fibers  ;     do      showing   young   branches   and 

flowers  from  the  nodes. 

they     get     any    more     abundant 

toward  the  base  ?  Do  any  of  them  pass  into  the  spine 
clusters?  What  do  the  spines  represent?  What  is  the 
use  of  the  green  layer  just  under  the  epidermis?  Why 
is  it  so  much  more  abundant  in  the  cactus  than  in  ordinary 
stems  ?  Lay  aside  a  section  of  a  cactus  plant,  or  a  leaf 
of  yucca,  agave,  or  other  fleshy  xerophyte  to  dry  and  see 
how  long  it  takes  to  lose  its  moisture.  What  would  you 
conclude  from  this  as  to  its  retentive  power  ? 

352.  Other  Xerophyte  Adaptations. —  Plants  exposed  to 
periodic  and  occasional  droughts  frequently  provide  against 
hard  times  by  laying  up  stores  of  nourishment  in  bulbs  and 
rootstocks  and  retiring  underground  until  the  stress  is  over. 
This  is  known  to  botanists  as  the  geophilons,  or  earth-loving 
habit.  Others,  as  some  of  the  lichens,  and  the  little  resur- 
rection fern  (Polypodium  incanum\  so  common  on  the 
trunks  of  oaks  and  elms,  make  no  resistance,  but  wither 
away  completely  during  dry  weather,  only  to  waken  again 
to  vigorous  life  with  the  first  shower. 


ECOLOGY 


472 
471,  472.  —  A  resurrection  fern  :  471,  in  dry  weather;  472,  after  a  shower. 

353.  Mesophytes.  —  These  embrace  the  great  body  of 
plants  growing  under  ordinary  conditions,  which  may  vary 
from  the  liberal  moisture  of  low  meadows  and  shady  forests 


PLANT   SOCIETIES 


247 


to  the  almost  xerophytic  barrenness  of  dusty  lanes  and  gul- 
lied hillsides.  The  forms  and  conditions  they  present  are 
so  diversified  that  it  will  be  impossible  even  to  touch  upon 
them  all  in  a  work  like  this,  but  they  may  be  summed  up 
under  the  two  principal  heads  of  open  ground  and  wood- 
land growth.  Under  the  first  are  included  all  cultivated 
grounds ;  fields,  lawns,  meadows,  pastures,  and  roadsides, 
with  their  characteristic  weeds,  flowers,  and  grasses.  Under 
the  second,  all  woods  and  copses  with  the  shrubs  and  herbs 
that  form  their  undergrowth. 

354.  Halophytes  include  plants  growing  by  the  seashore 
and  the  vegetation  around  salt  springs  and  lakes  and  that  of 
alkali  deserts.  Seaweeds  are  in  a  sense  halophytes,  since 
they  live  in  salt  water,  but  as  they  are  true  aquatic  plants 
and  exhibit  many  of  the  peculiarities  of  hydrophytes  in 
their  mechanical  structure,  they  are  classed  with  them. 
The  name  halophyte  applies  more  particularly  to  land 
plants  that  have  adapted  themselves  to  the  presence  of 
certain  minerals,  popularly  known  as  salts,  in  the  soil  or  in 
the  atmospheric  vapor.  If  you  have  ever  spent  any  time 
at  the  seashore,  you  can  not  fail  to  have  been  struck  with 
the  thick  and  fleshy  habit  exhibited  by  many  of  the  plants 
growing  there,  such  as  the  samphire,  sea  purslane  (Sesu- 
vium\  and  sea  rocket  (Cakile}.  A  form  of  goldenrod 
found  by  the  seashore  has  thick,  fleshy  leaves,  and  is  as 
hard  to  dry  as  some  of  the  fleshy  xerophytes. 

Another  characteristic  of  desert  plants  that  is  common 
also  to  seaside  vegetation,  is  the  frequent  occurrence  of  a 
thick,  hard  epidermis,  as  in  the  sea  lavender  and  saw 
grass.  The  live  oaks,  trees  that  love  the  salt  air  and 
never  flourish  well  beyond  reach  of  the  sea  breezes,  have 
small,  thick,  hard  leaves,  very  like  those  of  the  stunted 
oaks  that  grow  on  the  dry  hills  of  California.  The 
presence  of  spines  and  hairs,  it  will  be  observed,  is  also 
very  common ;  e.g.  the  salsola,  the  sea  ox-eye,  and  the 
low  primrose  (CEnothem  humifusa}.  In  other  cases  the 
leaf  blades  are  so  strongly  involute  or  revolute  (Sec.  60) 


248  ECOLOGY 

as  to  make  them  appear  cylindrical  —  an  arrangement 
for  protecting  the  stomata  (Fig.  98)  and  preventing  tran- 
spiration. All  these,  it  will  be  observed,  are  xerophyte 
characteristics,  and  the  object  in  both  cases  is  the  same 
—  economy  of  moisture.  The  reason  why  such  adapta- 
tions are  necessary  in  halophyte  plants  is  because  the 
mixture  of  salt  in  the  water  of  the  soil  increases  its 
density  so  that  it  is  difficult  for  the  plant  to  absorb  what 
it  needs  (Sec.  227).  Hence,  halophytes  are  in  the  con- 
dition of  Coleridge's  "Ancient  Mariner";  with  "water, 
water  everywhere,"  they  are  practically  living  under 
xerophyte  conditions. 

PRACTICAL  QUESTIONS 

1.  Why  do  florists  always   cultivate  cactus  plants  in  poor  soil? 

(35°-) 

2.  What  would  be  the  effect  of  copious  watering  and  fertilizing  on 
such  a  plant?     (350.) 

3.  Why  must  an  asparagus  bed  be  sprinkled  occasionally  with  salt? 
(348,  354-) 

4.  If  a  gardener  wished  to  develop  or  increase  a  fleshy  habit  in  a 
plant,  to  what  conditions  of  soil  and  moisture  would  he  subject  it? 
(35°>  354-) 

5.  What  difference  do  you  notice  between  blackberries  and  dew- 
berries grown  by  the  water  and  on  a  dry  hillside  ? 

6.  Is  there  a  corresponding  difference  between  the  root,  stem,  or 
leaves  of  plants  growing  in  the  two  situations,  and  if  so  account  for  it? 

7.  When  a   tract   of  dry  land  is  permanently  overflowed   by  the 
building  of  a  dam  or  levee,  why  does  all  the  original  vegetation  die,  or 
take  on  a  very  sickly  appearance?     (349.) 

8.  Should  plants  with   densely  hairy  leaves  be  given  much  water, 
as  a  general  thing?     (68,  350.) 

9.  A  farmer  planted  a  grove  of  pecan  trees  on  a  high,  dry  hilltop  ; 
had  he  paid  much  attention  to  ecology? 

10.    Give  a  reason  for  your  answer. 

FIELD  WORK 

Ecology  offers  the  most  attractive  subject  for  field  work  of  all  the 
departments  of  botany.  It  can  be  studied  anywhere  that  a  blade  of 
vegetation  is  to  be  found.  In  riding  along  the  railroad  there  is  an 
endless  fascination  in  watching  the  different  plant  societies  succeed  one 


PLANT   SOCIETIES  249 

another  and  noting  the  variations  that  they  undergo  with  every  change 
of  soil  or  climate. 

Students  in  cities  can  study  ecology  in  parks  and  public  squares,  in 
the  vegetation  that  springs  up  on  vacant  lots,  around  doorsteps  and 
area  railings,  and  even  between  the  paving  stones  of  the  more  retired 
streets.  A  botanist  found  on  a  vacant  lot  near  the  public  library  in 
Boston  over  thirty  different  kinds  of  weeds  and  herbs,  and  in  the  heart 
of  Washington,  D.C.,  on  a  vacant  space  of  about  twelve  by  twenty 
feet,  nineteen  different  species  were  counted.  Even  in  great  cities  like 
London  and  New  York,  one  occasionally  recognizes  among  the  rare 
weeds  struggling  for  existence  with  the  paving  stones  in  out-of-the-way 
corners,  some  old  acquaintance  of  fields  and  roadsides  far  away.  Just 
where  all  these  things  came  from,  and  how  they  got  there,  and  why 
they  stay  there,  will  be  interesting  questions  for  city  students  to  solve. 

But  the  country  always  has  been  and  always  will  be  the  happy  hunt- 
ing ground  of  the  botanist.  All  the  factors  considered  in  the  two  pre- 
ceding sections  can  hardly  be  found  in  any  one  locality,  but  mesophyte 
and  hydrophyte  conditions  exist  almost  everywhere,  and  approxima- 
tions to  the  xerophyte  state  can  generally  be  found  at  some  season  in 
open,  sandy,  or  rocky  places,  along  the  borders  of  dry,  dusty  roads,  and 
on  the  sun-baked  soil  of  old  red  hills  and  gullies. 

If  there  are  any  bodies  of  water  in  your  neighborhood  (in  cities, 
visit  the  artificial  lakes  in  parks),  examine  their  vegetation  and  see  of 
what  it  consists.  Notice  the  difference  in  the  shape  and  size  of  floating 
and  immersed  leaves  and  account  for  it.  Note  the  general  absence  of 
free-swimming  plants  in  running  water,  and  account  for  it.  Note  the 
difference  between  the  swamp  and  border  plants  and  those  growing  in 
the  water,  and  what  trees  or  shrubs  grow  in  or  near  it.  Compare  the 
vegetation  of  different  bogs  and  pools  in  your  neighborhood,  and 
account  for  any  differences  you  may  observe ;  why,  for  instance,  does 
one  contain  mainly  rushes,  sedges,  and  cat-tails,  another  ferns  and 
mosses,  another  sagittaria,  boneset,  water  plantain,  etc.,  and  still 
another  a  mixture  of  all  kinds?  Compare  the  water  plants  with  those 
growing  in  the  dryest  and  barrenest  places  in  your  vicinity,  note  their 
differences  of  structure,  and  try  to  find  out  what  special  adaptations  have 
taken  place  in  each  case. 

Draw  a  map  of  some  locality  in  your  neighborhood  that  presents 
the  greatest  variety  of  conditions,  representing  the  different  ecological 
regions  by  different  colored  inks  or  crayons,  or  by  different  degrees  of 
shading  with  the  pencil. 


X.    SEEDLESS   PLANTS 

THEIR  PLACE  IN  NATURE 

355.  Order  of  Development.  —  All  the  forms  that  have 
hitherto  claimed  our  attention  belong  to  the  great  division 
known  as  Spermatophytes,  or  seed-bearing  plants,  some- 
times designated  also  as  Phanerogams,  or  flowering  plants. 
They  comprise  the  higher  forms  of  vegetable  life,  and 
because  they  are  more  striking  and  better  known  than  the 
other  groups,  they  have  been  taken  up  first,  since  it  is 
easier  for  ordinary  observers  to  work  their  way  backwards 
from  the  familiar  to  the  less  known. 

But  it  must  be  understood  that  this  is  not  the  order  of 
nature.  The  geological  record  shows  that  the  simplest 
forms  of  life  were  the  first  to  appear  and  from  these  all 
the  higher  forms  were  gradually  evolved.  There  is  no 
sharp  line  of  division  between  any  of  the  orders  and 
groups  of  plants,  but  the  line  of  development  can  be 
traced  through  a  succession  of  almost  imperceptible 
changes  from  the  lowest  forms  to  the  highest,  and  it 
is  only  by  a  study  of  the  former  that  botanists  have 
come  to  understand  the  true  nature  and  structure  of  the 
latter. 

It  would  be  impossible,  in  a  work  like  this,  to  attempt 
even  a  superficial  view  of  the  various  divisions  of  seedless 
plants.  Many  of  them  are  of  microscopic  size,  and  can  not 
be  studied  without  expensive  laboratory  appliances  and 
skill  in  the  manipulation  of  the  microscope,  which  not 
everybody  can  possess.  A  short  study  of  only  a  few  typi- 
cal forms  will  be  attempted  here,  in  order  to  make  clearer 
some  of  the  processes  of  plant  life  that  have  already  been 
touched  upon. 

250 


THEIR   PLACE   IN   NATURE 


251 


473.  —  A  seaweed 
with  broad  expanded 
thallus. 


356.  Classification.  —  Beginning  with  the  lowest  forms, 
seedless  plants   are  grouped  into  three  great  orders,  or 
classes. 

357.  I.  Thallophytes,  or  thallus  plants. 
This    group   takes   its   name  from  the 
thallus  structure  that  characterizes  its 
vegetation.     What  a  thallus  is  will  be 
better  understood  after  a  specimen  has 
been  examined.     It  may  be  stated,  how- 
ever, that  the  term  is  applied  in  general 
to  the  simplest  kinds  of  vegetable  struc- 
ture, in  which  there  is  no  differentiation 
of   tissues,  and   no   true   distinction  of 
root,  stem,  and  leaves.     While  it  is  not 
peculiar    to    the    thallophytes,    it    has 

attained  its  most  typical  development  among  them,  and 
the  name  is  therefore  retained  as  distinctive  of  that  group. 
It  embraces  two  great  divisions,  the  Algae  and  Fungi. 
The  first  includes  seaweeds  and  the  common  fresh-water- 
brook  silks,  pond  scums,  etc.,  besides  numerous  micro- 
scopic forms  whose  presence  escapes  the  eye  altogether, 
or  is  made  known  only  by  the  discolorations  and  other 
changes  they  effect  in  the  water. 

To  the  fungi  belong  the  mushrooms 
and  puff  balls,  the  molds,  rusts, 
mildews,  etc.,  and  the  vast  tribe  of 
microscopic  organisms  called  bac- 
teria, that  are  so  active  in  the  pro- 
duction of  fermentation,  putrefaction, 
and  disease. 

358.    II.  Bryophytes,  or  moss  plants. 
474.  -  Anthoceros,    a    This    group    likewise    contains    two 
liverwort  with  flat,  spread-    divisions,     mosses     and     liverworts. 

ing  thallus.  ,  .        . 

Familiar  examples  of   the  latter  are 

the  marchantia,  or  umbrella  liverwort  (Figs.  500,  5O2)> 
commonly  found  on  the  ground  in  cool  bogs,  and  the  flat, 
spreading  plants,  bearing  somewhat  the  aspect  of  lichens, 


252 


SEEDLESS   PLANTS 


except  for  their  color,  met  with 
everywhere  on  wet  rocks  and 
banks  around  shady  water  courses. 

Mosses  are  one  of  the  best  de- 
nned of  botanical  orders,  and  are 
too  well   known 
to   need   further 
specification 
here. 

Bryophytes 
form  a  connect- 


ing link,  or  rath- 

475- —  Scapania,  a  liverwort     er      a      chain      of 
with  leafy  thallus,  approaching  .  .    . 

the  form   of  mosses  and  lyco-     Connecting    links 

podiums     (from     COULTER'S    between  the  next 

"Plant  Structures"). 

group,      ptendo- 

phytes,  and  thallophytes.  The  liverworts 
represent  the  more 
primitive  division  of 
the  group,  and  in  some 
of  their  forms  ap- 
proach so  near  the 
thallophytes  that  it 
does  not  take  a  bot- 
anist to  recognize  the 
relationship. 


477.  —  A    common    fern 


359.  III.  Pterido- 
phytes,  or  fern  plants, 
include  the  three  divi-  476.  — A  common 

-    r  ,  moss  plant,  with  parts 

SlOnS    Of    ferns,    horse-  apparently  divided  into 

tails,  and  club  mosses.  root- stem-  and  leaves- 

_,  ,.„  but  with  no  true   dif- 

They  differ  greatly  in  ferentiation    of     tis- 

structure,  but  all  pos-  sues  (from  COULTER'S 
"Plant  Structures"). 

sess    a    vascular    sys- 
tem,  a  well-organized  system   of   root, 
stem,  and  leaves,  and  rank  next  to  the 
spermatophytes  in  the  order  of  develop- 


FERN   PLANTS 


253 


merit.  They  are  frequently  distinguished  as  the  vascular 
cryptogams  to  differentiate  them  from  the  other  two 
groups,  cryptogams  being  a  term  sometimes  used  to  desig- 
nate the  three  orders  of  seedless  plants.  The  distinction 


478.  —  A  water  pteridophyte.  Marsilia  479.  —  Part  of  the  fruiting 

(after  GRAY).  stem    of    a    scouring   rush, 

Equisctum     limosuwi     (after 

GRAY). 

between  vascular  and  non-vascular  plants  is  relatively  as 
important  a  one  as  that  between  vertebrates  and  inverte- 
brates in  the  animal  kingdom. 

Just  what  these  three  great  groups  are,  and  what  relation 
they  bear  to  one  another,  will  be  better  understood  by  the 
study  of  a  typical  specimen  of  each. 

FERN  PLANTS 

MATERIAL.  —  Any  kind  of  fern  in  the  fruiting  stage.  The  pretty 
little  ebony  fern  (Asplemum  ebeneuni),  and  the  Christmas  fern 
(Aspidittm  acrosticheitUs)  are  common  almost  everywhere,  the  former 
on  shady  hillsides  near  the  foot  of  rocks  and  stumps,  or  in  the  shadow 
of  walls  and  fences ;  the  latter  in  rocky  woods  and  along  water  courses 


254 


SEEDLESS   PLANTS 


almost  everywhere.  City  schools  can  supply  themselves  with  speci- 
mens by  cultivating  a  few  ornamental  ferns  in  the  schoolroom.  While 
gathering  specimens  look  along  the  ground  under  the  fronds,  or  in 
greenhouses  where  ferns  are  cultivated,  among  the  pots  and  on  the  floor, 
for  a  small,  heart-shaped  body  like  that  represented  in  Figures  493,  494, 
-called  •a.prothallium.  It  is  found  only  in  very  wet  places  and  care  must 
be  taken  in  collecting  specimens,  as  in  their  early  stages  the  prothalli 
bear  a  strong  resemblance  to  certain  liverworts  found  in  the  same 
places.  The  best  way  is  for  each  class  to  raise  its  own  specimens  by 
scattering  the  spores  of  a  fern  in  a  glass  jar,  on  the  bottom  of  which  is 
a  bed  of  moist  sand  or  blotting  paper.  Cover  the  jar  loosely  with  a 
sheet  of  glass  and  keep  it  moist  and  warm,  and  not  in  too  bright  a  light. 
Spores  of  the  sensitive  ferns  (Onoclea)  will  germinate  in  from  two  to 
ten  days,  according  to  the  temperature.  Those  of  the  royal  fern 
{Osnmnda)  germinate  promptly  if  sown  as  soon  as  ripe,  but  if  kept 
even  for  a  few  weeks  are  apt  to  lose  their  vitality.  The  spores  of 
sensitive  fern  can  be  kept  for  six  months  or  longer,  while  those  of  the 
bracken  (Pterts)  and  various  other  species  require  a  rest  before  ger- 
minating, so  that  in  these  cases  it  it  better  to  use  spores  of  the  previous 
season. 

360.  Study  of  a  Typical  Fern.  —  Observe  the  size  and 
general  outline  of  the  fronds,  and  note  whether  those  of 
the  same  plant  are  all  alike,  or  if  they  differ  in  any  way, 
and  how.  Observe  the  shape  and  texture  of  the  divisions 
or  pinnae  composing  the  frond,  their  mode  of  attachment 
to  the  rhachis,  and  whether  they  are  simple,  or  notched  or 
branched  in  any  way.  Make  a  sketch,  labeling  the  pri- 
mary branches  of  the  frond,  pinna  (sing,  pinna},  the 
secondary  ones,  if  any,  pinnules,  and  the  common  stalk 
that  supports  them,  stipe.  Note  the  color,  texture,  and 
surface  of  the  stipe.  If  any  appendages  are  present,  such 
as  hairs,  chaff,  or  scales,  notice  whether  they  are  most 
abundant  toward  the  apex  or  the  foot  of  the  stipe,  or 
equally  distributed  over  its  whole  length.  Cut  a  cross 
section  near  the  foot  and  look  through  your  lens  for  the 
roundish  or  oblong  dots  that  show  where  the  fibrovascular 
bundles  were  cut  through  (Fig.  482).  How  many  of  them 
do  you  see  ?  Make  a  sketch  and  compare  with  your  sec- 
tional drawings  of  the  stems  of  monocotyledons  and 
dicotyledons ;  what  differences  do  you  notice  ?  Which 
does  it  resemble  most  ? 


FERN   PLANTS 


255 


Examine  the  mode  of  attachment  of  the  stipes  to  their 
underground  axis.  Break  one  away  and  examine  the  scar. 
Compare  with  your 
drawings  of  leaf  scars 
and  with  Figure  274. 
Do  the  stipes  grow 
from  a  root  or  a 
rhizoma  ?  How  do 
you  know  ?  Do  you 
find  any  remains  of 
leafstalks  of  previous 
years  ?  How  does 
the  rootstock  in- 
crease in  length  ? 
Measure  some  of 
the  internodes  ;  how 
much  did  it  increase 
each  year?  Cut  a 
cross  section  and  look 
for  the  ends  of  the 
fibrovascular  bun- 

Trace       their 

thrnno-h     *PV 
OUgn     S6V- 

eral  internodes.       Do 

they  run  straight  or 

do  they  turn  or  bend  in  any  way  at  the  nodes  ?      If 

where  do  they  go  ? 

361.  Veining.  —  Hold  a  pinna  up  to  the  light  and  ex- 
amine the  veining.     Is  it  like  any  of  the  kinds  described 
in  Sections  37-40  ?     This  forked  venation  is  a  very  general 
characteristic  of  the  ferns.     When  the  forks  do  not  reticu- 
late or  intercross  in  any  way,  the  veins  are  said  to  be  free  ; 
are  they  free  in  your  specimen,  or  reticulated  ? 

362.  Fructification.  —  Examine  the  back  of  the  frond; 
what  do  you  find  there  ?     (Most  ferns  bear  many  sterile 
fronds  ;  care  must  be  taken  to  secure  some  fruiting  ones.) 
These  dots  are  the  son  (sing.  sorns\  or  fruit  clusters,  and 


dles. 


480-484.  —  A  fern  plant:  480,  fronds  and  root- 
stock;  481,  fertile  pinna:  s,  s,  soii;  482,  cross 
section  of  a  stipe,  showing  ends  of  the  fibrovascular 
bund,es;  483,  a  cluster  of  sporangia,  magnified; 
484,  a  single  sporangium  still  more  magnified, 

sliedding  its  spores' 


so, 


256 


SEEDLESS    PLANTS 


485.  —  Part  of 
a  fertile  pinna  of 
polypodium  en- 
larged, showing 
the  sori  without 
indusium. 


486.  —  Part  of 
a  pinna  of  pellea 
enlarged,  showing 
indusium  formed 
by  the  revolute 
margin. 


the  fronds  or  pinnae  bearing  them  are  said  to  be  fertile. 

Are  there  any  differences  of  size,  shape,  etc.,  between  the 
fertile  and  sterile  fronds  of  your  specimen  ? 
Between  the  fertile  and  sterile  pinnae  ?  On 
what  part  of  the  frond  are  the  fertile  pinnae 
borne  ?  Notice  the  shape  and 
position  of  the  sori,  and  their 
relation  to  the  veins,  whether 
borne  at  the  tips,  in  the  forks, 
on  the  upper  side  (toward  the 
margin)  or  the  lower  (toward 
the  midrib).  Look  for  a  deli- 
cate membrane  (indnsiuni) 
covering  the  sori,  and  observe 
its  shape  and  mode  of  attach- 
ment. (If  the  specimen  under 

examination  is  a  polypodium  there  will  be  no  indusium ; 

if  a  maidenhair  (Adi- 
ant  mn\  or  a  bracken 

(Pteris\  it  will  be  formed 

of   the  revolute    margin 

of  the  pinna.)     In  lady 

fern    (Aspleninm    Filix- 

faemina),  and  Christmas 

fern  (Aspidium),  the  sori 

frequently  become    con-  48? 

fluent     that    i«      <tr>     oWp,  487>  488.  — Christmas   fern    (Aspidium): 

.ni,    Q  IS,    Si  J  487.  part  of  a  fertile  frond,  natural  size;  488, 

together  as  to  appear  like  a  Pinna  enlarged,  showing  the  sori  confluent 

T  •  j  under  the  peltate  indusia. 

a  solid  mass.     Sketch  a 

fertile  pinna  as  it  appears  under  the  lens,  bringing  out 

all  the  points  noted. 

363.  The  Spore  Cases.  — Look  under  the  indusium  at 
the  cluster  of  little  stalked  circular  appendages  (Fig.  483). 
These  are  the  sporangia,  or  spore  cases,  in  which  the 
reproductive  bodies  are  borne.  Seen  under  the  micro- 
scope each  sporangium  looks  like  a  little  stalked  bladder 
surrounded  by  a  jointed  ring  (Fig.  484).  At  maturity  the 


FERN   PLANTS  257 

ring  straightens  itself  out,  ruptures  the  wall  of  the  spo- 
rangium, and  the  spores  are  discharged  with  considerable 


49°  49i  492 

489-492.  — Spores  of  pteridophytes,  magnified  :  489,  a  fern  spore ;  490,  491,  two 
views  of  a  spore  of  a  club  moss;  492,  spore  of  a  common  horsetail  (Equisetum 
arveuse) . 

force.  Compare  the  spores  depicted  in  Figures  489-492, 
with  the  pollen  grains  in  Figures  378-381.  Do  you  notice 
any  resemblance  ? 

364.  Reproduction.  —  The   spores   are  the  reproductive 
bodies  of  ferns,  and  correspond  in  this  respect  to  the  seeds 
of  spermatophytes,  but  their  mode  of  reproduction  is  very 
different,   or  rather  seems  so,   because  here  the  process 
known  as  alternation  of  generations  first  becomes  apparent 
to  the  eye,  as  we  proceed  from  the  higher  plants  to  the 
lower.     The  same  thing  occurs  among  seed  plants  also, 
but  as  it  is  there  partly  concealed  within  the  seed,  botanists 
first  became  acquainted  with  it  through  the  study  of  spore- 
bearing  plants,  where  it  is  more  clearly  revealed.     What  is 
meant  by  it  will  be  better  understood  after  the  life  history 
of  the  ferns  has  been  studied. 

365.  The  Sporophyte.  —  The  spores  found  in  such  abun- 
dance on  the  fertile  pinnae  are  all  alike,  and  each  one  is 
capable  of  germinating  and  continuing  the  work  of  repro- 
duction without  the  necessity  of  any  such  union  as  we  saw 
taking  place  between   the  pollen  and   the   ovule   in   the 
spermatophytes.     The  plant  or  part  of  a  plant  that  bears 
these  reproductive  bodies  is  called  a  sporopliyte,  or  spore 
plant,  and  with  its  crop  of  spores  makes  up  one  generation. 

366.  The  Prothallium.  —  When  one  of  these  spores  ger- 
minates, it  produces,  not  a  fern  plant  like  the  one  that 
bore  it,  but  a  small,  heart-shaped  body  like  that  shown  in 

ANDREWS'S  EOT. —  17 


258 


SEEDLESS    PLANTS 


Figure  493,  called  a  prothallium.  Examine  one  of  these 
bodies  carefully  with  a  lens.  Observe  that  there  are  no 
Veins  nor  fibrovascular  bundles,  and  the  whole  body  of  the 
plant  seems  to  consist  of  one  uniform  tissue.  Some  little 
rootlike  hairs,  called  rhizoids,  will  be  found  growing  on 
the  under  side,  but  these  are  shown  by  the  microscope 

to  be  mere  appendages 
of  the  epidermis  in  the 
nature  of  hairs,  and  not 
true  roots.  Such  a  body 
as  this,  in  which  there 
is  no  differentiation  of 
parts,  is  what  consti- 
tutes a  thallus.  It 
occurs  in  all  kinds  of 
plants  under  varying 
forms,  and  different 
names  are  given  to  it. 
In  the  ferns  it  is  called 
a. prothallium.  In  them 
it  is  generally  short- 
lived and  is  important  only  in  connection  with  the  work 
of  reproduction.  Note  its  heart-shaped  outline,  and  look 
just  below  the  deep  notch  at  the  apex  for  certain  little 
bottle-shaped  bodies  called  archegonia.  (They  will  prob- 
ably appear  under  the  lens  as  mere  dots,  or  may  not  be 
visible  at  all.)  These  correspond  to  the  pistils  of  seed 
plants.  Lower  down,  among  the  rhizoids,  or  near  the 
margin  of  the  prothallium,  are  certain  organs,  called  antJie- 
ridia,  corresponding  to  the  stamens  of  spermatophytes. 

367.  The  Gametophyte.  —  The  reproductive  cells  con- 
tained in  the  antheridia  and  archegonia  are  called  gametes 
and  from  them  the  prothallium  is  called  a  gamctophyte,  or 
gamete  plant,  in  contradistinction  to  the  sporophyte  or 
spore  plant.  The  gametes  differ  from  ordinary  spores  in 
not  being  able  to  perform  the  work  of  reproduction  directly 
by  germination,  but  a  pair  of  them  must  first  unite  and  form 


493,  494.—  Prothallium  of  a  common  fern 
(Asfidium)  :  493,  under  surface,  showing 
rhizoids,  rh,  antheridia,  an,  and  archegonia, 
ar\  494,  under  surface  of  an  older  game- 
tophyte,  showing  rhizoids,  rh,  and  young 
sporophyte,  with  root,  w,  and  leaf,  b  (from 
COULTER'S  "Plant  Structures"). 


FERN   PLANTS  259 

another  kind  of  spore  called  an  oospore,  which  is  capable 
of  germinating.  It  reproduces,  however,  not  the  simple 
thalluslike  gametophyte  from  which  it  sprang,  but  the 
beautiful  fern  plant,  or  sporophyte,  with  its  vascular  system 
and  complete  outfit  of  vegetative  organs  —  root,  stem, 
and  leaves. 

368.  Alternation    of    Generations.  —  We    all    know   the 
meaning  of  the  word  generation  as  applied  to  the  direct 
descendants  of  one  organism  from  another,  whether  animal 
or  plant.    When  two  successive  generations  produce  respec- 
tively ordinary  spores  and  oospores,  and  these  different 
kinds  of  spores  give  rise  to  organisms  unlike  in  structure 
or  habits   of    life,  there  is   said  to  be   an   alternation  of 
generations.    The  generation  which  bears  the  simple  spores 
(sporophyte)  is  said  to  be  asexual;  the  one  which  produces 
the  gametes  and  oospores  is  sexual ;  that  is,  it  requires  the 
union  of  two  separate  bodies  to  produce  a  fertilized  germ, 
or  oospore.     Each  generation,  therefore,  it  will  be  observed, 
gives  rise  to  its  opposite,  the  asexual  sporophyte  producing 
the  sexual  gametophyte,  or  prothallium,  and  this  in  turn, 
through  its  gametes  and  oospores  reproducing  the  asexual 
sporophyte.      The  alternation   in   ferns  may,  in  general, 
be  expressed  to  the  eye  by  a  series  of  diagrams  like  those 
given  below.     The  words  in  each   line  are  synonyms  of 
those  immediately  above  or  below  them  in  the  other  lines, 
except  it  must  be  observed  that,  strictly  speaking,  it  is 
not   the    antheridia   and    archegonia,    but    the    spores   or 
gametes  contained  in  them  that  by  their  union  produce 
the  oospore. 

Fern  plant  — >- Spores -»-  Prothallium  -*-(  ^^          &S~*~ Oospore—*-  Fern  plant. 

\Antheiidia  / 

Sporophyte  — >-  Spores  -*-  Gametophyte  — >-  <^  G    ngte  /  ~~*"~  O6sPore  "*"  sP°r°Phyte- 
Asexual  gen. ->- Spores  — >- Sexual  gen.— ^\G^^/~ >- Oospores ->-  Asexual  gen. 

369.  Advantages     of    Alternation.  —  This    roundabout 
mode  of  reproduction  would  hardly  have  been  developed 


260 


SEEDLESS   PLANTS 


unless  it  had  been  of  some  benefit  to  the  plants  practicing 
it.  The  chief  advantage  seems  to  be  in  more  rapid  mul- 
tiplication and  consequently  better  chance  to  propagate  the 
species.  Only  one  plant  is  produced  by  each  oospore,  and 
if  this  were  a  gametophyte  with  its  limited  number  of 
archegonia,  multiplication  would  be  slow;  but  the  sporo- 
phyte  with  its  millions  of  spores,  each  capable  of  produc- 
ing a  new  individual,  enables  the  species  to  multiply 
indefinitely.  On  the  other  hand,  the  interposition  of  a 
gametophyte,  or  sexual  generation,  secures  the  introduc- 


495-499-  — A  kind  of  pteridophyte  (Selaginella  martensii)  with  its  organs  of 
fructification :  495,  a  fruiting  branch ;  496,  a  microsporophyll  with  a  microsporan- 
gium,  showing  microspores  through  a  rupture  in  the  wall ;  497,  a  megasporophyll 
with  a  megasporangium ;  498,  megaspores;  499,  microspores  (from  COULTER'S 
"  Plant  Structures"). 


FERN    PLANTS  261 

tion  of  a  new  strain  at  each  alternation,  with  the  advan- 
tages of  cross-fertilization  (Sec.  312). 

370.  Microspores  and  Macrospores.  —  The  method  of  re- 
production in  other  pteridophytes  is  similar  in  all  essentials 
to  that  of  the  ferns,  except  that  in  some  of  the  orders  it 
is  even  more  complicated.  The  sporophyte,  instead  of 
producing  spores  which  are  all  alike,  bears  two  kinds  of 
fruiting  organs  called  sporophylls  (spore-bearing  leaves), 
one  of  which  produces  sporangia  containing  large  bodies 
called  mcgaspores,  or  macrospores,  the  other  smaller  ones 
called  microspores.  These  large  and  small  spores  give  rise 
to  different  kinds  of  gametophytes,  one  bearing  arche- 
gonia,  the  other  antheridia,  and  it  is  only  by  the  union  of 
a  pair  of  gametes  from  each  kind  that  an  oospore  capable 
of  producing  another  sporophyte  can  originate.  This 
complicated  arrangement  may  be  expressed  to  the  eye  by 
a  diagram  something  like  the  following,  in  which  5  stands 
for  sporophyte,  G  for  gametophyte,  ings,  for  megaspore, 
vies,  for  microspore,  mgsph.  for  megasporophyll,  mcsph.  for 
microsporophyll,  gam.  for  gamete,  and  oo.  for  oospore. 

/  mgsph.  — >-  mgs.  — >-  archegonial  G.  — >•  gam.V ^_  Q&  ^    e(c 

'  ~~^\ mcsph.  — >-  mcs.  — >-  antheridial  G.  — >-  gam.  / 


PRACTICAL  QUESTIONS 

1.  Have  ferns  any  economic  use  — that  is,  are  they  good  for  food, 
medicines,  etc.? 

2.  What  is  their  chief  value? 

3.  Under  what  ecological  conditions  do  they  grow? 

4.  Are  they  often  attacked  by  insects,  or  by  blights  and  disease  of 
any  kind? 

5.  Of  what  advantage  is  it  to  ferns  to  have  their  stems  under  ground, 
in  the  form  of  rootstocks?    (195.) 

6.  What  causes  the  young  frond  of  ferns  to  unroll?    (162,  204.) 

7.  Name  the  ferns  indigenous  to  your  neighborhood. 

8.  Which  of  these  are  most  ornamental  and  to  what  peculiarities  of 
structure  do  they  owe  that  quality  ? 

9.  Are  cultivated  ferns  usually  raised  from  the  spores  or  in  some 
other  way?     Why? 


262 


SEEDLESS  PLANTS 
STUDY  OF  A  BRYOPHYTE 


MATERIAL. Any  of  the  common  thalloid  or  flat-bodied  liverworts. 

They  can  generally  be  found  growing  with  mosses  on  wet,  dripping  rocks 
and  the  shady  banks  of  streams,  and  are  easily  recognized  by  their  flat, 
spreading  habit,  which  gives  them  the  appearance  of  green  lichens. 
Marchantia  polymorpha  (Fig.  500),  one  of  the  largest  and  best  speci- 
mens for  study,  is  common  in  shady,  damp  ground  throughout  the  north- 


500.  — Umbrella  liverwort  {Marchantia  polymorpha)  ;  portion  of  a  thallus  about 
natural  size,  showing  dichotomous  branching:  f,f,  archegonial  or  female  recep- 
tacles ;  r,  rhizoids. 

ern  States.  Lunularia,  a  smaller,  species  that  can  be  recognized  by 
the  little  crescent-shaped  receptacles  on  some  of  the  divisions  of  the 
thallus,  is  abundant  in  greenhouses  almost  everywhere,  on  the  floor,  or 
on  the  sides  of  pots  and  boxes  kept  in  clamp  places.  Specimens  of  this 
can  be  procured  by  city  classes,  but  the  spore-bearing  receptacles  are 
seldom  or  never  present,  the  species  being  an  introduced  one  and  possi- 
bly rendered  sterile  by  changed  conditions.  Marchantia  polymorpha 
is  the  specimen  described  in  the  text,  but  any  allied  species  will  do. 


STUDY   OF   A   BRYOPHYTE 


263 


371.    Examination  of  a  Liverwort. — The  Thallus.     The 

broad,  flat,  branching  organ  that  forms  the  body  of  the 

plant  is  the   thallus.      Examine 

the  end  of  each  branch;    what 

do  you  find  there  ?     Are  the  two 

forks  into  which  the  apex  of  the 

branches    divide    equal    or    un- 
equal ?      Do    you    see    anything 

in  these  forking  apexes  to  remind 

you  of  the  heart-shaped  prothal- 

lium  of  the  fern  ?     Are  there  any 

other     points     of     resemblance 

between    them  ?      Compare   the 

growing  end  with  the  distal  one  ; 

does  it  proceed  from  a  true  root  ? 

Notice  that  as  the  lower  end  dies 

the  growing  branches  go  on  increasing  and  reproducing 

the  thallus. 

Do  you  find  anything  like  a  midrib  ?     If   so,  trace  it 

along  the  branches  and 
stem  ;  where  does  it  end  ? 
Does  it  seem  to  be  formed 
like  the  midrib  of  a  dicoty- 
ledon ?  Hold  a  piece  of 


the    upper 


501.  — Under  side  of  an  arche- 
gonial  receptacle  enlarged.  The 
archegonia  are  borne  among  the 
hairs  on  the  under  surface,  which 
is  presented  to  view  in  the  figure ; 
/  a  spore  case. 


503.  —  porton  o  te  upper 
epidermis  of  marchantia,  magnified, 
showing  rhomboidal  plates  with  a 


stoma  in  each. 

the  thallus  up  to  the  light 
and  see  if  you  can  detect 

502.  —  Portion  of  a  thallus  hiring  an  any  veins.  Is  it  of  the 
antheridial  disk  or  receptacle,  d,  and  gem-  game  co]or  jn  a]|  parts  an(J 
m3e-^.^-  .._ 

if  there  is  a  difference  can 

you  give  a  reason  for  it  ?     Examine  the  upper  surface  with 
a  lens.     Peel  off  a  piece  of  the  epidermis,  place  it  between 


SEEDLESS   PLANTS 


two  moistened  bits  of  glass  and  hold  it  up  to  the  light,  keep- 
ing the  upper  surface  toward  you ;  what  is  its  appearance  ? 
Observe  a  tiny  dot  near  the  center  of  the  rhomboidal 
areas  into  which  the  epidermis  is  divided  and  compare  it 
with  your  drawings  of  stomata  (Sec.  16).  What  should 
you  judge  that  these  dots  are? 

372.  Rhizoids.  —  Wash  the  dirt  from  the  under  side  of  a 
thallus  and  examine  with  a  lens ;  how  does  it  differ  from 
the  upper  surface  ?  Observe  the  numerous  rootlike  hairs, 
or  rhizoids.  What  is  their  color  ?  Where  do  they  spring 
from  ?  These  are  not  true  roots,  but  hairs  that  have  taken 
upon  themselves  the  function  of  absorption,  and  do  not 
imply  any  actual  differentiation  of  tissues. 

Plant  a  growing  thallus  branch  in  moist  earth  so  that 
the  upper  side  will  lie  next  the  soil  and  watch  for  a  week 
or  two,  noting  what  changes  take  place.     What  would  you 
infer  from  this  as  to  the  cause 
of  the  difference  between  the 
two  surfaces  ?     Would  rhizoids 
be  of  any  use  on  the  upper  side  ? 
Stomata  on  the  under  side  ? 

373.  Gemmae.  —  Look  along 
the  upper  surface  of  some  of 
your  specimens  for  little  saucer- 
shaped  (in  Lunularia,  crescent- 
shaped)  cupules  or  cavities. 
Notice  the  border,  whether  it 

7.-Lunularia,  a  common      ^    tO°thed    °F   Cntire>  and   S6e   if 
livenvort :  504,  portion  of  a  thallus     yOU    Can    tell    what    the    CUpuleS 

Sos^'fertne^lant  wiUi^fmUm^      contain-         These     little     bodies, 

receptacles;  506,  an  enlarged  sec-    called  gemma,  are  a  kind  of  bud, 

tion  of  one  of  the  fruiting  recepta- 
cles ;  507,  portion  of  a  sterile  thallus 
slightly  enlarged,  showing  one  of 

the  crescent-shaped   gemmae  from  j  , ,  1M       i      i  r 

which  the  plant  takes  its  name.  and  the  tiger  Illy  do  by  means  of 

bulblets.  Sow  some  of  the  gem- 
mae on  moist  sand,  cover  them  with  a  tumbler  to  prevent 
evaporation,  and  watch  them  develop  the  thalloid  structure. 


by  which  the  plant  propagates 
itself    somewhat   as   the   onion 


STUDY   OF  A   BRYOPHYTE  265 

374.  Reproduction  by  Spores.  —  If  possible,  procure  a 
thallus  with  upright  pedicels  bearing  enlargements  at  the 
top  like  those  represented  in  Figures  500  and  502.  These 
are  receptacles  containing  spore  cases  corresponding  to  the 
archegonia  and  antheridia  of  the  fern  prothallium.  Notice 
their  difference  in  form,  the  one  (Fig.  502)  umbrella  shaped 
and  scalloped  round  the  edges,  the  other  (Fig.  500)  rayed, 
like  the  spokes  of  a  wheel.  The  first  produce  antheridia 
only,  and  the  second  archegonia.  Examine  both  surfaces 
of  each,  and  then  vertical  sections,  under  a  lens.  Notice 
that  the  antheridia  grow  from  the  upper  surface  of  the 
scalloped  disks,  the  archegonia  from  the  underside  of  the 
rayed  ones,  concealed  in  the  heavy  covercles  that  depend 
from  the  rays  (Fig.  501).  The  archegonia  and  antheridia, 
as  in  the  ferns,  produce  different  kinds  of  reproductive 
cells  called  gametes,  and  so  the  thallus  that  forms  the  plant 
body  of  the  liverwort  is  the  gametophyte  and  corresponds 
to  the  prothallium  of  the  fern.  When  one  of  the  gametes 
from  an  antheridium  enters  an  archegonium  and  fuses 
with  the  other  kind  of  gamete  contained  there,  an  oospore 
is  formed  as  in  the  fern,  which  is  capable  of  germinating 
and  producing  a  new  growth.  But  instead  of  falling  to 
the  ground  and  giving  rise  to  an  independent  plant  like  the 
sporophyte  of  the  fern,  the  oospore  germinates  within  the 
receptacle  and  produces  there  an  insignificant  spore  case 
(f,  Fig.  501),  containing  ordinary  spores  and  thus  repre- 
senting in  a  reduced  form  the  sporophyte  that  is  so  conspic- 
uous a  feature  of  the  ferns.  These  spores,  on  germinating, 
produce  the  liverwort  thallus  body  or  gametophyte,  thus 
completing  the  cycle  of  generations.  Notice  that  in  the 
liverwort  (and  all  bryophytes),  the  thallus  or  gametophyte, 
is  the  important  part  of  the  plant  and  performs  all  the 
vegetative  functions,  while  the  sporophyte  is  a  small,  insig- 
nificant body  that  never  becomes  detached  from  the  game- 
tophyte and  has  no  independent  existence.  In  the  fern 
and  other  pteridophytes  just  the  reverse  is  true ;  the  sporo- 
phyte constitutes  the  beautiful  plant  body  that  we  all  admire 
so  much,  while  the  gametophyte,  though  it  does  attain  a 


266  SEEDLESS    PLANTS 

separate  existence,  appears  only  as  an  obscure  prothallium 
that  is  usually  as  short  lived  as  it  is  inconspicuous. 

375.  Alternation  of  Generations  in  Seed  Plants.  —  While 
the  alternation  of  generations  is  more  conspicuous  in 
pteridophytes  and  bryophytes,  it  occurs  also  among  the 
algse,  and  is  universal,  though  in  a  masked  form,  among 
the  spermatophytes.  It  is  therefore  very  important  to 
have  a  clear  idea  of  what  it  means,  for  the  chief  turning 
points  in  the  life  history  of  all  plants  are  connected  with 
it,  and  the  natural  relationships  of  the  different  groups 
and  their  distribution  according  to  those  relationships 
depend  largely  upon  a  comparison  of  the  reproductive 
processes  in  the  various  classes  and  orders.  These  studies 
are  too  intricate  and  technical  to  be  even  outlined  here ; 
suffice  it  to  say  that  some  of  the  gymnosperms  —  pines, 
yews,  cycads,  etc.  —  show  striking  similarities  in  their  repro- 
ductive processes  to  those  of  the  higher  pteridophytes,  and 
through  them  a  repetition  of  the  most  salient  features  of 
the  alternation  of  generations  in  the  highest  seed  plants 
has  been  traced.  Briefly  stated,  we  may  say  that  the 
stamens  of  spermatophytes,  and  the  pistils,  or  rather  the 
carpels,  which  we  saw  to  be  transformed  leaves,  represent 
the  sporophylls  (Sec.  370)  of  the  higher  pteridophytes. 
The  pollen  sacs  and  ovules  are  sporangia,  bearing  micro- 
spores  and  megaspores  (Sec.  370),  represented  respec- 
tively by  the  pollen  grains  in  the  anther  and  the  embryo 
sac  in  the  ovule.  These  go  through  a  series  of  micro- 
scopic changes  in  the  body  of  the  ovule  analogous  to  the 
production  of  the  oospore  in  the  archegonia  of  ferns  and 
liverworts,  but  the  process  is  so  obscure  that  to  an  ordinary 
observer  the  pollen  grains  and  ovule  appear  to  be  the  real 
gametes,  and  were  supposed  to  be  such,  by  the  older  bota- 
nists. The  fertilized  germ  cell  in  the  embryo  sac  (Sec.  327) 
corresponds  to  an  oospore,  the  endosperm  found  in  all 
seeds  (previous  to  its  absorption  by  the  cotyledons)  is  a 
rudimentary  gametophyte,  and  the  embryo  in  the  matured 
seed,  the  undeveloped  sporophyte,  destined,  after  germina- 


THE    ALG.E  26/ 

tion  and  further  growth,  to  produce  a  new  generation  of 
microspores;  i.e.  pollen  grains,  and  megaspores  (embryo 
sac),  and  so  on,  through  the  cycle. 

376.  Relative  Importance  of  Gametophyte  and  Sporophyte. 

—  It  is  important  to  notice  that  the  progressive  diminution 
of  the  gametophyte  in  comparison  with  the  sporophyte 
which  we  saw  taking  place  in  proceeding  from  the  bryo- 
phytes  to  pteridophytes,  reaches  its  climax  in  the  spermato- 
phytes,  where  it  is  reduced  to  such  insignificance  that  it  is 
only  by  certain  analogies  of  structure  and  function  that  it 
can  be  recognized  at  all.  It  remains  permanently  inclosed 
within  the  walls  of  the  ovary  and  is  absorbed  by  the  sporo- 
phyte during  germination,  or  even  earlier  in  those  seeds 
classed  as  ex-albuminous.  The  sporophyte,  on  the  other 
hand,  represents  the  fully  organized  plant,  and  attains 
among  dicotyledons  the  highest  development  of  vegetable 
structure. 

THE  ALGM 

MATERIAL.  —  Collect  in  a  bottle  some  of  the  green  scum  found  in 
stagnant  pools,  ditches,  and  sluggish  streams  everywhere,  and  vari- 
ously known  as  frog  spit,  pond  scum,  brook  silk,  etc.  In  cities  and 
other  places  where  specimens  are  not  easily  procured,  it  can  be  culti- 
vated in  a  simple  aquarium  made  of  a  wide-mouthed  glass  jar  with  a 
few  pebbles  and  sticks  at  the  bottom. 

377.  Variety  of  Forms.  —  This  group  embraces  plants 
of  the  greatest  diversity  of  form  and  structure,  from  the 
minute  volvox  and  desmids  that  hover  near  the  uncertain 
boundaries  dividing  the  vegetable  from  the  animal  world, 
to  the  giant  kelps  of  the  southern  ocean,  which  sometimes 
attain  a  length  of  from  six  hundred  to  one  thousand  feet. 
The  fresh-water  algae  are  all  very  small,  and  those  of  them 
that  are  visible  to  the  naked  eye  belong  mostly  to  the  fila- 
mentous group,  so  called  from  their  slender  threadlike  thalli, 
that  look  like  bits  of  fine  green  floss  floating  about  in  the 
water. 

378.  Examination  of  a  Specimen.  —  Place  a  drop  or  two 
of  fresh  pond  scum  on  a  piece  of  glass  and  examine  with 


268 


SEEDLESS    PLANTS 


a  lens.  Of  what  does  it  appear  to  consist  ?  Are  the  fila- 
ments all  alike,  or  are  they  of  different  lengths  and  thick- 
ness ?  Soak  a  number  of  them  in  alcohol  for  half  an  hour 
and  examine  again;  where  has  the  green  matter  gone? 
Do  these  algae  contain  chlorophyll?  (Sec.  25). 

379.  Spirogyra.  —  The  filamentous  algae  are  very  numer- 
ous, and  your  drop  of  pond  scum  will  probably  contain  sev- 
eral kinds.     At  least  one  of  these,  it 
is  likely,  will  be  a  Spirogyra,  as  this 
is  one  of  the  commonest  and  most 
widely  distributed  of  them  all.     This 
genus  takes  its  name  from  the  spiral 
bands    in  which    the    chlorophyll   is 
usually   disposed    (Fig.    508)  within 
the  cells.     These  bands  are  single  in 
some  species,  in  others  they  combine 
and  intercross  in  various  ways,  form- 
ing   most    beautiful    patterns    when 

formation  of  viewed  under  the  microscope.  Each 
filament  is  seen,  when  sufficiently 
magnified,  to  consist  of  a  number  of  more  or  less  cylin- 
drical cells  joined  together  in  a  vertical  row,  and  thus 
forming  the  simple  threadlike  thallus  that  characterizes 
this  class  of  algae.  Physiologically,  each  cell  is  an  inde- 
pendent individual,  and  often  exists  as  such. 

380.  Vegetative  Multiplication.  —  Some  of  the  algae,  so 
far  as  our  present  knowledge  goes,  have  only  the  one  form 
of  reproduction  known  as  vegetative  multiplication,  or  fis- 
sion (splitting).     A  cell  divides  itself  in  two,   each  half 
grows  into  a  distinct  cell,  which  again  divides,  forming 
new  cells,  and  so  on,  till  millions  of  individuals  may  result 
from  a  single  mother  cell  in  a  few  days,  or  in  some  cases, 
in  a  few  hours.     This  method  of  reproduction  takes  place 
in  some  form  or  other  in  almost  all  plants,  the  propagation 
by  buds,  tubers,  rootstocks,  runners,  etc.,  among  sperma- 
tophytes  being  nothing  but  a  mode  of  vegetative  multi- 
plication. 


THE 


269 


381.  Conjugation.  —  Another  method  of  reproduction  is 
by  the  formation  of  spores.     In  spirogyra  and  many  other 
algae  the  spores  are  formed  by  the  method  known  as  con- 
jugation, that  is,  joining  together.     The  cells  of  two  adja- 
cent filaments  send  out  lateral  protuberances  toward  each 
other  (Fig.  509),  and  when  the  ends  of  these  protuber- 
ances meet,  the  protoplasm  in  each  contracts,  the  contents 
of  one  pass  over  into  the  other,  the  two  coalesce  and  form 
a  new  cell  but  little,  if  any,  larger  than  the  original  con- 
jugating bodies.      This  cell   germinates   under  favorable 
conditions  and  produces  a  new  individual. 

382.  Diatoms  and  Desmids.  —  These  two  groups  are  alike 
in  their  microscopic  size,  in  their  simple  structure,  and  in 
the  interest  that  attaches  to  them  on    account   of  their 
enormous  numbers  and  their  great  beauty  and  variety  of 
form,  but  otherwise  they  are   not   nearly  related  orders. 
The   diatoms   are   so   different  from  all   other  vegetable 
structures  that  they  are 


i         ••  ., 


510  511  s«  S'3 

510-513.  — Diatoms  (highly  magnified): 
510,  511,  Grammatophora  serpentina ;  512, 
513,  Fragllaria  vircscens. 


placed  by  some  bota- 
nists in  a  class  to  them- 
selves ;  others  group 
them  among  the  algae. 
They  consist  of  simple 
cells  inclosed  in  a  very 
hard  mineral  covering 
formed  of  two  valves,  one  of  which  fits  over  the  other  like 
the  lid  of  a  pasteboard  box.  They  are  of  a  brown  color 
and  of  almost  every  conceivable  shape  (Figs.  510-513). 
Not  less  than  ten  thousand  species  have  been  described, 
and  immense  deposits  of  rock  in  various  parts  of  the 
world  are  formed  by  the  flinty  coverings  of  millions  of 
these  microscopic  creatures  that  once  floated  in  the  seas 
of  past  geologic  ages. 

The  desmids  were  for  a  long  time  classed  with  animals, 
but  have  now  been  handed  over  definitively  to  the  botanist. 
They  are  of  a  bright  green  color,  and  are  further  distin- 
guished from  the  diatoms  by  their  perfect  bilateral  sym- 


2/0 


SEEDLESS   PLANTS 


metry ;  that  is,  both  sides  of  a  cell  are  just  alike.  They 
are  found  only  in  fresh  water ;  diatoms  inhabit  either  salt 
water  or  fresh. 


514  515 

514-517.  —  Desmids  (highly  magnified)  :  514.  Micrasterias papillifera  ;  515,  Micra- 
sterias  morsa  ;  516,  Cosmarium  polygonum  ;  517,  Xanthidium  aculeatum. 

383.  Place  in  Nature.  —  Algae  exist  in  vast  multitudes 
both  as  to  the  number  of  species  and  of  individuals.  They 
all  contain  chlorophyll,  but  in  a  few  fresh-water  forms 
and  in  most  seaweeds  it  is  obscured  by  pigments  of  brown 
or  red  to  which  the  brilliant  coloration  of  these  plants  is 
due.  The  presence  of  these  pigments  probably  has  some 
relation  to  their  peculiar  environment,  especially  in  the 
case  of  those  growing  in  deep  water,  where  the  action  of 
light  upon  the  chlorophyll  is  greatly  diminished  and  altered 
by  refraction.  Their  variations  in  color  form  a  convenient 
basis  of  classification,  and  botanists  divide  algae  into  six 
great  orders,  according  to  their  color.  The  spirogyra  and 
most  fresh-water  species  belong  to  the  order  of  Cliloro- 
phycea,  or  Green  Algae.  This  class  is  of  special  interest 
because  from  it  all  the  higher  forms  of  vegetable  life  are 
believed  to  have  been  derived. 

PRACTICAL  QUESTIONS 

1.  Are  any  of  the  green  algae  parasitic  ?    How  do  you  know  ?    (25.) 

2.  What  is  their  effect  upon  the  atmosphere  ;    that  is,  do  they  tend 
to  purify  it  by  giving  off  oxygen,  or  the  reverse  ?     (24,  25.) 

3.  Why  is  their  presence  in  water  regarded  as  denoting  unhygienic 
conditions  ? 

4.  Refer  to  the  experiment  in  Section  22,  and  account  for  the  bub- 
bles and  froth  that  usually  accompany  these  plants  in  the  water. 

5.  Can  you  suggest  any  other  causes  than  the  elimination  of  oxygen 
that  might  produce  the  same  effect  ? 

6.  Is  the  presence  of  these  gas  bubbles  of  any  use  to  the  plants  ? 

7.  Should  you  expect  to  find  parasites  among  the  green  algae  ?  Why  ? 


XI.     FUNGI 

THEIR   CLASSIFICATION 

384.  What  is  a  Fungus?  — The  fungi  are  all  (with  a 
few  doubtful  exceptions)  parasites  or  saprophytes  which 
have  lost  their  chlorophyll  and  become  incapable  of  sup- 
porting an  independent  existence.     Biologists  are  divided 
as  to  their  position  in  the  genealogical  tree  of  life.     The 
weight  of  authority  at  present  seems  to  incline  to  the  view 
that  they  are  degenerate  forms  derived   from  the  algae, 
while  others  regard  them  not  as  degraded  descendants  of 
higher  forms,  but  as  representatives  of  the  lowest  primor- 
dial types  from  which  higher  organizations   have  arisen. 
If  they  represent  a  degraded  and  degenerate  type,  they 
have  been  so  modified  by  their  parasitic  habits  as  greatly 
to  obscure  their  relationship  and  render  their  position  in 
the  general  scheme  of  life  a  very  doubtful  one.     They 
represent  an  offshoot,  or  side  branch  as  it  were,  of  the 
great  evolutionary  line,   and  so  will  be  considered  in  a 
chapter  by  themselves. 

385.  Economic   Importance.  —  On  account  of  their  im- 
mense numbers,  reaching  at  present  the  enormous  total  of 
forty-five  thousand  known  species,  and  of  the  parasitic  habit, 
which  causes  them  to  enter  the  bodies  of  other  plants  and 
of  animals,  fungi  are  of  great  economic  importance,  espe- 
cially the  various  microscopic  forms  grouped  under  the 
head  of  Bacteria.      These,  by  their  rapid  multiplication 
within  the  blood  and  the  tissues  of  their  victims,  produce 
the  most  fatal  and  destructive  diseases.    They  are  the  small- 
est living  organisms,  and  are  always  floating  in  the    tmos- 
phere,  so  that  with  every  breath  we  draw,  large  numbers 

271 


272  FUNGI 


of  them  are  inhaled.     Fortunately,  however,  most  of  them 
are  harmless,  unless   inhaled  in  very  great  numbers   or 


o"  $0    fco.V 

s'8  519 

518,  519.  —  Milk  (highly  magnified)  :  518,  pure,  fresh  milk;  519,  milk  that  has 
stood  for  hours  in  a  warm  room  in  a  dirty  dish,  showing  fat  globules  and  many 
forms  of  bacteria. 

under  certain  unhealthful  conditions,  while  a  few,  such  as 
the  yeast  fungus  and  the  bacteria  concerned  in  the  pro- 
cesses of  decomposition,  are  very  useful.  The  presence  of 


520  521  522  523 

520-523.  —  Forms  of  bacteria :  520,  bacteria  of  consumption  (Bacillus  tubercu- 
losis) •  521,  cholera  bacillus;  522,  bacilli  of  anthrax,  showing  spores;  523,  typhoid 
bacillus. 

bacteria  in  the  soil  is  also  of  importance  sometimes,  since 
through  their  agency  the  nitrogen  compounds  are  rendered 
soluble  by  the  roots  of  plants  (Sec.  198). 

386.  Difficulty  of  Classification.  —  The  life  history  of 
fungi  in  general  is  very  obscure  and  difficult  to  trace,  both 
on  account  of  the  microscopic  size  of  the  great  majority  of 
them,  and  of  the  curious  habit  of  polymorphism  exhibited 
by  many  species;  that  is,  the  same  individual  appears 
under  entirely  different  forms  at  different  stages  of  its  ex- 


MUSHROOMS 


2/3 


istence,  like  an  insect  undergoing  metamorphosis,  so  that 
it  is  often  impossible  to  tell  whether  a  given  specimen 
belongs  to  a  distinct  group  or  is  merely  a  form  of  the  same 
species  at  a  different  stage  of  its  existence. 

Our  knowledge  of  them  being  so  imperfect,  their  classi- 
fication is  in  great  confusion,  and  any  grouping  of  them 
must  be  considered  as  in  a  great  measure  provisional  only. 


PRACTICAL  QUESTIONS 

1.  Why  ought  preserved  fruits  and  vegetables  to  be  scalding  hot 
when  put  into  the  can ?     (385.) 

2.  Why  is  it  necessary  to  exclude  the  air  from  them?     (385.) 

3.  Why  does  using  boiled  water  for  drinking  render  a  person  less 
liable  to  disease?     (142,  385.) 

MUSHROOMS 

MATERIAL.  —  Any  kind  of  gilled  mushroom  in  different  stages  of 
development,  with  a  portion  of  the  substratum  on  which  it  grows,  con- 
taining some  of  the  so-called  spawn.  In  city  schools  the  common  mush- 
room sold  in  the  markets  (Agaricus  campestris)  can  usually  be  obtained 
without  difficulty.  It  would  be  advisable  to  buy  some  of  the  spawn  and 
raise  a  crop  in  the  schoolroom,  as  then  all  parts  of  the  plant  would  be 
on  hand  for  examination.  Full  directions  for 
cultivating  this  fungus  are  given  in  Bulletin 
53  of  the  U.S.  Department  of  Agriculture. 
From  six  to  twelve  hours  before  the  lesson 
is  to  begin,  cut  the  stem  from  the  cap  of  a 
mature  specimen  close  up  to  the  gills,  lay 
the  gills  downward  on  a  piece  of  clean  paper, 
cover  them  with  a  bowl  or  pan  to  keep  the 
spores  from  being  blown  about  by  the  wind 
and  leave  them  until  a  print  (Fig.  532)  has 
been  formed. 

387.  Examination  of  a  Typical 
Specimen.  —  The  most  highly  spe- 
cialized of  the  fungi,  and  the  easiest 
to  observe  on  account  of  their  size 
and  abundance,  are  the  mushrooms 
that  are  such  familiar  objects  after 
every  summer  shower.  The  gilled 
kind  —  those  with  the  rayed  laminae  voiva. 

ANDREWS'S  EOT.— 1 8 


524.  — Deadly  agaric  (Ama- 
nita  phalloides),  showing  the 
broad  pendent  annulus,  a, 
formed  by  the  ruptured  veil, 
the  cup  at  the  base,  c,  and 


2/4 


FUNGI 


under  the  cap  —  are  usually  the  most  easily  obtained. 
Gather  a  specimen  of  some  of  these  according  to  the 
directions  given  above,  and  examine  them  as  soon  as 
possible,  since  they  decay  very  quickly. 

388.  The  Mycelium.  —  Examine  some  of  the  white 
fibrous  substance  usually  called  spawn,  through  a  lens. 
Notice  that  it  is  made  up  of  fine  white 
threads  interlacing  with  each  other, 
and  often  forming  webby  mats  that 
ramify  to  a  considerable  distance 
through  the  substratum  of  rotten  wood 
or  other  material  upon  which  the 
fungus  grows.  These  threads  are 
^  called  hypluBy  and  are  apt  to  be  mis- 
taken for  roots,  but  they  are  really 
the  thallus  or  true  vegetative  body 
of  the  plant,  the  part  rising  above 
ground  and  usually  regarded  as  the 

525.  —  Mycelium    of    a      *  J         ° 

mushroom  (Agaricus  cam-    mushroom,    being   only  the  fruit,  or 

testns)  with  young  buttons    ^productive   organ.     The  thallus  of 

(fruiting  organs)  in  differ-       f  .    .  f 

ent  stages :  i,  2, 3>  4, 5,  sec-    all  fungi  is  called  a  mycehum  from 

Greek  word 


opment ;  m,  mycelium  ;  st, 

stipe; /,  piieus; /,  gill,  or  389.  The  Button.  —  Look  on  the 
mycelium  for  one  of  the  small  round 
bodies  called  buttons  (Fig.  525).  These  are  the  beginning 
of  the  fruiting  body,  popularly  known  as  the  mushroom, 
and  are  of  various  sizes,  some  of  the  youngest  being 
barely  visible  to  the  naked  eye.  After  a  time  they  begin 
to  elongate  and  make  their  way  out  of  the  substratum. 

390.  The  Veil  and  Volva.  —  Make  a  vertical  section 
through  the  center  of  one  of  the  larger  buttons  after  it  is 
well  above  ground,  and  sketch.  Notice  whether  it  is  en- 
tirely enveloped  from  root  to  cap  in  a  covering  membrane  — 
the  volva  (Fig.  526,  a) — or  whether  the  enveloping  mem- 
brane extends  only  from  the  upper  part  of  the  stem  to  the 
margin  of  the  cap  —  the  veil  (Fig.  526,  d)\  whether  it  has 


MUSHROOMS 


275 


ill 


526.  —  Diagram  of  unexpanded  Ama- 
nita,  showing  parts  :  a,  volva ;  b,  pileus; 
c,  gills ;  d,  veil ;  e,  stipe ;  m,  mycelium. 


both  veil  and  volva,  or  finally  whether  it  is  naked,  that 
is,  devoid  of  both. 

Next  take  a  fully  expanded 
specimen  and  observe  k_.; 

391.  The  Stipe,  or  stalk. 
Notice  as  to  length,  thick- 
ness, color,  and  position, 
that  is,  whether  it  is  in- 
serted in  the  center  of  the 
cap  or  to  one  side  (excen- 
tric),  or  on  one  edge  (lateral). 
Observe  the  base,  whether 
bulbous,  tapering,  or  straight, 
and  whether  surrounded  by 
a  cup,  or  merely  by  con- 
centric rings  or  ragged  bits 
of  membrane  (the  remains 
of  the  volva).  Look  for  the  annulus  or  ring  (remains  of 
the  veil)  near  the  insertion  of  the  stipe 
into  the  cap,  and  if  there  is  one,  notice 
whether  it  adheres  to  the  stipe,  or 
moves  freely  up  and  down  as  in  Figure 
527,  a ;  whether  it  is  thick  and  firm,  or 
broad  and  membranous  so  that  it  hangs 
like  a  sort  of  curtain  round  the  upper 
part  of  the  stipe  (Fig.  524,  a).  Break 
the  stem  and  notice  whether  it  is  hollow 
or  solid,  observe  also  the  texture, 
whether  brittle,  cartilaginous,  fibrous, 
fleshy,  etc.  Next  observe  the 

392.  Pileus,  or  cap,  as  to  color  and 
surface,  whether  dry,  or  moist  and 
sticky;  smooth,  or  covered  with  scurf 
or  scales  left  by  the  remains  of  the 
volva,  as  it  was  stretched  and  broken 
up  by  the  expanding  cap  (Fig.  527, />,/).  Note  also  the 
size  and  shape,  whether  conical,  expanded,  funnel  shaped 


527.  —  Parasol  mifih- 
room  (Lepiota  procerd), 
showing  movable  an- 
nulus: st,  stipe;  a,  an- 
nulus, or  ring;  w.umbo; 
p,p,  floccose  patches  left 
by  volva. 


276 


FUNGI 


(infundibuliform,  Fig.  528);  umbonate,  having  a  protuber- 
ance at  the  apex  (Fig.  527),  etc; 
whether  the  margin  is  turned  up 
at  the  edge  (revolute,  Fig.  524), 
or  under  (involute,  Fig.  527).  Look 
at  the  under  surface  and  examine 

393.  The  Gills,  or  laminae.  — 
Notice  whether  they  are  broad 
or  narrow,  whether  they  extend 
straight  from  stem  to  margin  or 
are  rounded  at  the  ends,  or  are 
curved, 

3.  —  Chanterelle  (Cantka-  , 

rellus  cibarius),  with   infundi-  toothed, 

buliform  pileus  and  decurrent  or  lobed 
gills. 

in     any 

way.  Notice  their  attachment 
to  the  stipe,  whether  free,  not 
touching  it  at  all  ;  adnate, 
attached  squarely  to  the  stem 
at  their  anterior  ends  ;  or  decur- 
rent, running  down  upon  the 
stem  for  a  greater  or  less  dis- 
tance (Fig.  528). 

394.  The  Hymenium.  —  Cut 
a  tangential  section  through  one 
side  of  the  pileus  and  sketch 
as  it  appears  under  the  lens.  S29_53I._Sections  of  a  gilled 

If    a    very    thin    CrOSS    Section  Of     mushroom  :  529,  through  one  side, 

^  HS4  ^S 

53°.  one  of  tne  gills  more  enlarged, 

.-i-i  .       -,-,.  showing  the   central  tissue  of  the 

It  Will   appear  as   in   Figure  529.      trama>V.  and   the  broad   border 
More    highly  magnified    sections     formed  by  the  hymenium,/;;  531, 
,  .       ,-,.  a  small  section  of  one  side  of  a  gill 

are  shown  in  Figures  530,  531.    very  much  enlarged(  showing  the 

The  blade  of  the  gill,  Called   the     club-shaped  basidia,  b,  b,  standing 

at  right  angles  to  the  surface,  bear- 

trama,  is  covered  on  both  sides    ing  each  two  small  branches  with 
by  a  membranous  layer  bearing    a  sPore>  s<  s'  at  the  end-    The 

J  '      sterile    paraph  yses,    /,    are    seen 

elongated    Club-shaped    Cells    Set     mixed  with  the  basidia. 


one  of  the  gills  is   made  and 

placed     Under     the      microscope 


MUSHROOMS 


/ 
277 


upon  it  at  right  angles  to  the  surface  (Fig.  530).  Some 
of  these  put  out  from  two  to  four,  or  in  some  species  as 
many  as  eight  little  prongs,  each  bearing  a  spore  (Fig. 
531,  s,  s},  while  others  remain  sterile.  The  spore-bearing 
cells  are  called  basidia,  the  sterile  ones,  paraphyses,  and 
the  whole  spore-bearing  surface  together,  the  hymenium, 
from  a  Greek  word  meaning  a  membrane.  It  is  from  the 
presence  of  this  expanded  fruiting  membrane  that  the 
class  of  mushrooms  we  are  con- 
sidering gets  its  botanical  name, 
Hymenomycetes,  membrane  fungi. 

395.  Spore  Prints.  —  When 
the  gills  are  ripe  they  shed  their 
spores  in  great  abundance.  Take 
up  the  pileus  that  was  laid  on 
paper  as  directed  under  Material, 
on  page  273,  and  examine  the 
print  made  by  the  discharged  532- -Spore  print  of  a  giiied 

.,,    ,        ,  ,  .  mushroom. 

spores ;  it  will  be  found  to  give 

an  exact  representation  of  the  under  side  of  the  pileus. 
The   hymenium  is  not   always   borne   on   gills,  but  is 

arranged  in  various  ways  which  serve  as  a  convenient  basis 

for  distinguishing  the  different  orders.     In  the  Polyporei, 

to  which  the  edible 
boletus  belongs 
(Figs.  533,  534), the 
basidia  are  placed 
along  the  inside  of 
little  tubes  that  line 
the  under  side  of 
the  pileus,  giving 
it  the  appearance 

533. 534-  —  A  tube  fungus  (Boletus  edulis) :  533,  entire ;    of     a     honey COttlb. 
534,  section,  showing  position  of  the  tubes.  jn    another    order, 

the  porcupine  fungi,  they  are  arranged  on  the  outside  of 
projecting  spines  or  teeth,  while  in  the  morelles  they  are 
held  in  little  cups  or  basins. 


2/8 


FUNGI 


396.  The  Spores.  —  Notice  the   color   of   the  spores  as 
shown  in  the  spore  print.     This  is  a  matter  of  importance 
in  distinguishing  gill-bearing  fungi,  which  are  divided  into 
five  sections  according  to  the  color  of  the  spores.     One 
source  of  danger,  at  least,  to  mushroom  eaters  would  be 
avoided  if  this  difference  was  always  attended  to,  for  the 
deadly  amanita   (A.  phalloides},  and   the   almost  equally 

dangerous  fly  mushroom  (A.  mus- 
caria\  both  have  white  spores,  while 
the  favorite  edible  kind  {Agaricus 
campestris],  though  white  gilled  when 
young,  produces  dark,  purple-brown 
spores  that  can  not  fail  to  distin- 
guish it  clearly  for  any  one  who  will 
take  the  trouble  to  make  a  print. 

Sketch     a     longitudinal     section 
through  the  center  of  a  well-devel- 
535. -Diagram  of  a  gilled          d  mushroom,  as  shown  in  Figure 

mushroom. 

535,  labeling  the  different  parts  that 

you  can  distinguish,  and  bringing  out  as  well  as  you  can  the 
points  observed  in  your  examination  of  the  living  specimen. 

397.  Mushrooms  and  Toadstools.  —  The  popular  distinc- 
tion which  limits  the  term  "mushroom  "  to  a  single  species, 
the  Agaricus  campestris,  and  classes  all  others  as  toadstools, 
has  no  sanction  in  botany.     All  mushrooms  are  toadstools 
and  all  toadstools  are  mushrooms,  whether  poisonous  or 
edible.      The  real  distinction  is  between  mushrooms  and 
puff  balls,  the  former  term  being  more  properly  applied 
only  to  that  class  of  fungi  which  have  the  hymenium  or 
spore-bearing  surface  exposed. 

398.  Food  Value.  —  The  food  value  of  mushrooms  has 
been  greatly  exaggerated.     They  contain  a  large  propor- 
tion of  water,  often  over  ninety  per  cent,  and  the  most 
valued  of  them,  the  Agaricus  campestris,  bears  a  very  close 
resemblance  to  cabbage  in  its  nutrient  properties.     They 
are  pleasant  relishes,  however,  and  as  agreeable  articles 
of  diet,  are  not  to  be  despised. 


RUSTS 


PRACTICAL  QUESTIONS 


279 


1.  Why  are  mushrooms  generally  grown  in  cellars ?     (25,384.) 

2.  Name  any  fungi  you  know  of  that  are  good  for  food  or  medicine 
or  any  other  purpose. 

3.  Name  the  most  dangerous  ones  you  know  of. 

4.  Do  you  find  fungi  most  abundant  on  young  and  healthy  trees,  or 
on  old,  decrepit  ones  ?     Account  for  the  difference.     (384.) 

5.  Do  you  ever  find  them  growing  upon  perfectly  sound  wood  any- 
where? 

6.  Is  it  wise  to  leave  old,  unhealthy  trees  and  decaying  trunks  in  a 
timber  lot? 

RUSTS 

MATERIAL.  — A  leaf  of  wheat  affected  with  red  rust.  A  leaf  or  a 
stalk  with  black  rust.  Some  barberry  leaves  with  yellowish  pustules  on 
the  under  side  that  look  under  the  lens  like  clusters  of  minute  white 
corollas  (see  Fig.  542).  As  the  spots  on  barberry  occur  in  spring,  the 
red  rust  in  summer,  and  the  black  rust  in  autumn,  the  specimens  will 
have  to  be  gathered  as  they  can  be  found,  and  preserved  for  use. 

In  the  southern  States  barberry  occurs  but  rarely  or  not  at  all,  and  a 
different  species  of  rust,  the  orange  leaf  (Pucctnia  rubigo-vera),  is  more 
common  than  the  ordinary  wheat  rust  {Puccinia graminis),  but  the  two 
are  so  much  alike  that  the  directions  given  will  do  for  either.  If  the 
orange  leaf  rust  is  used,  the  cups  and  pustules  should  be  looked  for  on 
plants  of  the  borrage  family  —  comfrey,  hound' s-tongue,  etc.  Leaves 
of  oats  or  other  infected  grasses  may  be  used,  but  wheat  is  to  be  pre- 
ferred, as  the  life  history  of  the  common  wheat  rust  (/*.  Graminis) 
has  been  more  clearly  traced  than  that  of  any  other  variety.  The  apple 
scab  fungus  may  be  used  instead  of  wheat  if  more  convenient.  In  this 
case,  provide  apple  or  haw  leaves  affected  with  scab,  and  some  of  the 
common  excrescences  known  as  cedar  apples. 

399.  Red  Rust. —  Uredo  Stage.  Examine  a  leaf  of  "  red 
rusted  "  wheat  under  the  lens,  and  notice  the  little  oblong 
brown  dots  that  cover  it.  These  are  the  sori,  or  clusters 
of  sporangia  that  have  formed  upon  the  surface.  Viewed 
under  the  microscope  the  red  rust  is  seen  to  consist  of 
a  mycelium  that  ramifies  through  the  tissues  of  the  leaf 
and  bears  clusters  of  single-celled  reddish  spores  that 
break  through  the  epidermis  and  form  the  reddish  brown 
spots  and  streaks  from  which  the  disease  takes  its  name. 
These  spores,  falling  upon  other  leaves,  germinate  in  a  few 


280  FUNGI 

hours  and  form  new  mycelia,  from  which,  in  six  to  ten 
days,  fresh  spores  arise.  Formerly  this  was  thought  to 
complete  the  life  history  of  the  fungus,  to 
which  the  name  of  Uredo  was  given.  It  is 
now  known,  however,  that  the  red  rust  is 
merely  a  stage  in  the  life  cycle  of  the  plant, 
and  to  this  stage  the  old  name  uredo  is 
applied,  and  the  spores  are  called  uredo- 
spores. 

400.  Black  Rust.  —  Next  examine  with 
your  lens  a  part  of  the  plant  attacked  by 
black  rust.  Do  you  observe  any  difference 
except  in  the  color  ?  Do  the  two  kinds  of 
rust  attack  all  parts  of  the  plant  equally  ? 
If  not,  what  part  does  each  seem  to  affect 
more  particularly  ?  At  what 
S' 537  season  does  the  black  rust  ap- 

536,537.  — Leaf    pear  most  abundantly? 
*,h  "S       ^  ™i  formerly  supposed  that 
rust,  Puccinia  ru-    black    rust   was    caused    by   a 
stage^e  upper    different  fungus  from  that  pro- 
side  of  leaf;  537,    ducing  red  rust,  and  to  it  the 

under  side.  ,_,         .     .  .  , 

name  Pucctnia  was  given,  but 
it  is  now  known  to  be  only  another  phase  of 
the  same  parasite  that  produces  the  red  rust. 

TM.  «  T>          ••»»-,.•        j  i          538.  — Stalk 

The  name     Puccinia     is  retained  as  a  general    wjtn  pvccmia 
designation  for  all  fungi  undergoing  these  two    graminis,   te- 
phases,  and  the  particular  form  of  fungus  that 
we  are  now  considering  is  known  in  all  its  stages  as  Puc- 
cinia graminis. 

401.  Teleutospores.  —  Toward  the  end  of  summer  the 
same  mycelium  that  bore  the  uredospores  begins  to 
develop  the  dark  spore  clusters  that  give  to  black  rust  its 
characteristic  color  and  its  name.  After  this  the  uredo- 
spores soon  cease  to  be  developed  at  all,  and  only  the  dark 
ones  called  teleutospores  are  produced.  These  remain  on 
the  culms  in  the  stubble  fields  over  winter,  ready  to  begin 


RUSTS 


28l 


the  work  of  reproduction  in  spring,  whence  they  are  called 
"  winter  spores,"  in  contradistinction  to  the  uredos  or 
"summer  spores,"  whose  activity  seems  to  be  confined  to 
the  warm  months. 


539.  —  Uredospores  of  wheat  rust,  Puccinia  graminist  magnified  (from 
COULTER'S  "  Plant  Structures"). 

Under  the  microscope  the  teleutospores  appear  as  long, 
two-celled  bodies  with  very  thick  black  walls  (Fig.  540). 
Since  they  are  developed  from  the  same  mycelium  with  the 


540.  —  Teleutospores  of  wheat  rust,  magnified  (from  COULTER'S 
"  Plant  Structures  "). 

uredospores,  and  are  not  a  product  of  the  latter,  but  collat- 
eral with  them,  the  two  constitute  a  single  generation,  and 
belong  to  one  and  the  same  stage  in  the  life  history  of  the 
plant. 

402.  Sporidia,  —  In  spring  the  teleutospores  begin  to 
germinate,  each  cell  producing  a  small  filament,  from 
which  arise  in  turn  several  small  branches.  Upon  the  tip 


282 


FUNGI 


of  each  of  these  branches  is  developed  a  tiny  sporelike 
body  called  a  sporidium  (Fig.  541),  which  continues  the 
generation  of  the  rust  fungus  through 
the  next  stage  of  its  existence.  The  fila- 
ment which  bears  these  sporidia  is  not 
parasitic,  but  when  the  sporidia  ripen 
and  the  spores  contained  in  them  are 
scattered  by  the  wind,  there  begins  a 
second  parasitic  phase,  which  forms  the 
most  curious  part  of  this  strange  life 
history. 

403.  The  ^cidium.  —  Examine  now 
the  under  side  of  your  barberry  leaves 
(or  comfrey,  etc.,  if  red  rust  is  used),  for 
clusters  of  small  whitish  bodies  that 
appear  under  the  lens  like  little  white 
corollas  with  yellow 
anthers  in  the  center. 
More  highly  magni- 
fied, this  yellow  sub- 

stance is  seen  to  be  composed  of  regular 

layers  of  colored  spores.     The  corolla- 

like  receptacles  containing  them,  popu- 

larly  known    as    "  cluster    cups,"    are 

u  T  i  i    r 

borne  on  a  mycelium   produced  from 
the  spores  described  in  the  last  para- 

,          r^,  .  ,.  .  .  . 

graph.  This  mycelium  is  parasitic  on 
barberry  or  other  leaves,  according  to  the  kind  of  fungus, 
and  was  long  believed  to  be  a  distinct  plant,  to  which  the 
name  sEcidium  was  given.  This  term  (pi.  AZcidia)  is 
now  applied  to  the  cluster  cups,  and  those  fungi  which 
at  any  period  of  their  life  history  produce  them  are  called 
ALcidiomycetes,  ^Ecidium  fungi. 

404.    Connection  between  Barberry  and  Wheat  Rust.  — 

There  had  long  existed  a  popular  belief,  both  in  this  country 
and  in  England,  that  the  presence  of  barberry  bushes  near 
grain  fields  produced  rust,  or  mildew,  as  it  is  called  in  Eng- 


541.  —  Teleutospore 
germinating  and  form- 
ing sporidia,  s,s,  (from 
COULTER'S  "  Plant 
Structures"). 


542.  —  Cluster  cups  of 

app]e  rust  (Kosteiia),  the 
secidium   stage   of  the 

"  cedar  apple  "  fungus. 


RUSTS  283 

land.  There  is  a  village  in  Norfolk  that  long  went  by  the 
name  of  "  Mildew  Rollesby,"  on  account  of  the  mildewed 
grain  caused,  it  was  believed,  by  the  abundance  of  bar- 
berry bushes  in  the  neighborhood.  These  were  cut  down 
and  mildew  at  once  disappeared.  Repeated  instances  of 
the  kind  led  a  few  men  of  science  to  suspect  that  the  pop- 
ular belief  might  be  something  more  than  a  mere  supersti- 
tion, after  all.  Experiments  were  made  which  showed  that 
grain  planted  in  the  vicinity  of  a  barberry  bush  infected 
with  aecidia  developed  rust  immediately  after  the  aecidia 
spores  matured,  and  that  rust  was  most  abundant  in  the 
direction  in  which  the  wind  carried  the  spores.  Further 
experiment  showed  that  aecidia  spores  would  not  germinate 
directly  on  barberry ;  in  other  words,  aecidia  would  not  re- 
produce aecidia  directly,  but  only  after  passing  through  one 
or  more  intermediate  stages,  and  thus  it  was  proved  beyond 
a  doubt  that  these  fungi  are  not  independent  plants,  but 
merely  a  phase  in  the  life  history  of  the  Puccinia. 

405.  The  Life  Cycle. — Taking  the  first  phase  of  the 
season  as  our  starting  point,  the  life  cycle  of  the  wheat 
rust  consists  of  three  stages  carried  on  by  four  different 
kinds  of  spores:  (i)  The  non-parasitic  stage,  which  origi- 
nates from  teleutospores,  and  produces  sporidia ;  (2)  The 
aecidium  phase,  which  arises  from  the  sporidia,  is  parasitic 
on  barberry,  and  produces  spores  that  germinate  on  grain  ; 
(3)  The  uredo-teleuto  phase,  parasitic  on  grain.  The  first,  or 
sporidia  stage,  which  is  too  small  to  be  discoverable  except 
by  the  microscope,  escapes  the  notice  of  the  ordinary  ob- 
server, and  the  third,  producing  two  kinds  of  spores,  uredo 
and  teleuto,  has  the  appearance  of  being  two  separate 
stages,  so  that  to  one  unacquainted  with  the  facts,  the  life 
cycle  would  seem  to  consist  of  a  red  rust  or  uredo  stage,  a 
black  rust,  or  teleuto  stage,  and  an  aecidium  stage.  The 
last  is  often  omitted.  In  many  cases,  as  in  our  own  south- 
ern States,  where  there  are  no  barberries  to  act  as  hosts, 
the  sporidia  germinate  directly  upon  young  wheat,  without 
passing  through  the  cluster  cup  stage,  and  the  orange  leaf 


284 


FUNGI 


rust  is  known  to  be  capable  of  propagating  year  after  year 
in  the  uredo  stage  alone,1  the  spores  surviving  through  the 
winter  on  volunteer  grains  and  other  grasses. 

406.  Cedar  Apples.  —  An  excellent  subject  for  study  is 
the  common  fungus  (Gymnosporangiunt)  that  produces 
upon  red  cedar  twigs  the  large  excrescences  familiarly 
known  as  "  cedar  apples."  It  is  related  to  the  wheat  rusts, 
but  has  only  two  phases,  its  spores  germinating  and  pro- 


543.  —  Two  species  of  "  cedar  apple  "  (  Gymnosporangmiri) ,  showing  stage  of  the 
apple  rust  fungus  corresponding  to  the  uredo-teleuto  stages  of  wheat  rust  (from 
COULTER'S  "Plant  Structures"). 

ducing  aecidia  upon  the  leaves  of  apple,  hawthorn,  and 
other  kindred  plants.  In  this  stage  it  is  known  as  Rostelia, 
and  is  the  cause  of  apple  rust  and  other  similar  orchard 
diseases.  Specimens  are  generally  easy  to  obtain  and  can 
be  studied  by  the  same  methods  outlined  in  the  foregoing 
paragraphs. 

407.  Polymorphism.  —  Plants  that  pass  through  different 
stages  in  their  life  history  are  said  to  be  polymorphic,  that 

1  Bulletin  16,  United  States  Department  of  Agriculture. 


RUSTS  285 

is,  of  many  forms.  The  habit  is  very  common  among  the 
lower  forms  of  vegetation.  The  fact  that  one  or  more  of 
the  phases  are  sometimes  omitted,  as  the  aecidium  phase 
of  wheat  rust  in  warm  climates,  suggests  the  idea  that  it 
may  be  of  use  in  helping  the  plant  to  tide  over  difficult 
conditions.  Blackberry,  anemone,  groundsel,  buckthorn, 
and  many  other  common  plants  are  known  to  harbor 
aecidia,  but  what  particular  species  of  uredo  and  puccinia 
and  aecidium  belong  together  in  any  one  case,  it  is  impos- 
sible to  determine  without  continued  observation  and 
experiment. 

408.  Difference  between  Polymorphism  and  Alternation 
of  Generations.  —  These  two  processes  must  not  be  con- 
founded. A  polymorphic  plant,  so  far  as  we  know,  may 
reproduce  itself  indefinitely  by  means  of  simple  spores 
without  the  intervention  of  gametes  and  oospores,  but  to 
constitute  an  alternation  of  generations  there  must  inter- 
vene somewhere  in  the  life  history  the  union  of  two  unlike 
spores  (gametes)  to  form  an  oospore,  with  the  alternate 
appearance  of  sporophyte  and  gametophyte. 

PRACTICAL  QUESTIONS 

1.  Is  a  farmer  wise  to  leave  scabby  and  mildewed  weeds  and  bushes 
in  the  neighborhood  of  his  grain  fields?     (40?-) 

2.  Are  there  any  objections  to  the  presence  of  volunteer  grain  stalks 
along  roadsides  and  in  fence  corners  during  winter  ?     (405.) 

3.  Should  cedar  trees  be  allowed  to  grow  near  an  apple  orchard  ? 
Give  a  reason  for  your  answer.     (406.) 

4.  Should  diseased  plants  be  plowed  under?     (402.) 

5.  What  disposition  should  be  made  of  them? 

6.  Ought  diseased  fruits  be  left  hanging  on  the  tree? 

7.  Why  is  it  necessary  to  pick  over  and  discard  from  a  crate  or  bin 
all  decaying  fruits  and  vegetables  ? 

FIELD  WORK 

The  study  of  fungi  can  be  carried  on  only  to  a  very  limited  extent 
without  the  use  of  a  compound  microscope,  and  all  serious  work  of  the 
kind  must  be  conducted  in  the  laboratory.  The  general  observer,  how- 
ever, may  do  some  practical  work  by  learning  to  recognize  the  various 


286  SYSTEMATIC   BOTANY 

blights,  rusts,  mildews,  etc.,  by  their  effects  upon  the  vegetation  of  his 
neighborhood.  Learn  to  know  at  a  glance  whether  a  given  field  or  or- 
chard is  suffering  from  leaf  curl,  scab,  the  yellows,  bunt,  smut,  mildew,  etc. 
A  systematic  study  of  mushrooms  will  be  found  very  interesting  from 
both  a  scientific  and  a  dietetic  point  of  view  for  those  who  have  leisure 
to  undertake  it  and  means  to  expend  on  the  rather  costly  literature  that 
deals  with  the  subject. 

SYSTEMATIC  BOTANY 

409.  Now  that  some  knowledge  has  been  obtained  of 
the  structure  of  plants,  their  analysis  and  classification  can 
be  taken  up  with  both  profit  and  pleasure.     To  know  the 
place  of  a  species  in  the  great  scheme  of  life,  and  under- 
stand what  is  to  be  expected  of  it  in  its  normal  family 
relations  is  necessary  before  we  can  appreciate  justly  its 
adaptations  to  the  surrounding  conditions  in  its  struggle 
for  existence.     It  is  not  advisable  to  spend  too  much  time 
in  the  mere  identification  of  species,  but  enough  should  be 
examined  and  described  to  familiarize  the  student  with  the 
distinctive  characteristics  of  the  principal  botanical  groups. 

410.  Botanical  Terminology  is  in  a  very  unsettled  state  at 
present,  owing  to  disagreements  among  botanists  as  to  the 
use  of  certain  terms,  but  this  does  not  affect  the  general  prin- 
ciples of  classification  and  nomenclature.      All  the  known 
plants  in  the  world,  varied  and  multitudinous  as  they  are, 
numbering  not  less  than  one  hundred  and  twenty  thousand 
species  of  the  seed-bearing  kind  alone,  are  ranged  accord- 
ing to  certain  resemblances  of  structure,  into  a  number  of 
great  groups  known  as  families  or  orders.      The  names 
of  these  families  are   distinguished  by  the  ending  acece ; 
the  rose  family,  for  instance,  are  the  Rosacea ;  the  pink 
family,  Caryophyllacea  ;  the  walnut  family,  Juglandacecz,  etc. 

411.  Genera  and  Species.  —  Each   of   these   families  is 
divided  into  lesser  groups  called  genera  (singular,  genns\ 
characterized  by  similarities  showing  a  still  greater  degree 
of  affinity  than   that  which  marks  the  larger  groups   or 
orders;    and    finally,   when   the    differences   between   the 
individual  plants  of  a  kind  are  so  small  as  to  be  disre- 


SYSTEMATIC   BOTANY  287 

garded,  they  are  considered  to  form  one  species,  just  as  all 
the  common  morning-glories,  of  whatever  shade  or  color, 
belong  to  the  species  Ipomea  purpurea.  The  small  differ- 
ences that  arise  within  a  species  as  to  the  color  and  size  of 
flowers,  and  other  minor  points,  constitute  mere  varieties 
and  have  no  special  names  applied  to  them.  The  line 
between  varieties  and  species  is  not  clearly  defined,  and  in 
the  nature  of  things  can  never  be,  since  progressive  devel- 
opment, through  slow  but  unceasing  change,  is  the  law  of 
all  life. 

In  botanical  descriptions  the  name  both  of  the  species 
and  of  the  genus  is  given,  just  as  in  designating  a  person, 
like  Mary  Jones  or  John  Robinson,  we  give  both  the 
surname  and  the  Christian  name.  The  genus,  or  generic 
name,  answers  to  the  surname,  and  that  of  the  species  to 
the  Christian  name  —  except  that  in  botanical  nomencla- 
ture the  order  is  reversed,  the  generic,  or  surname  coming 
first,  and  the  specific  or  individual  name  last ;  for  example, 
Ipomea  is  the  generic,  or  surname,  of  the  morning-glories, 
and  purpurea  the  specific  one. 

412.  How  to  use  the  Key.  —  Any  good  manual  will  do  ; 
Gray's  "  School  and  Field  Book  "  is  perhaps  the  best  avail- 
able at  present  for  the  States  east  of  the  Mississippi.  A 
little  reference  to  what  has  already  been  said  on  the  subject 
of  classification  in  Sections  126-129,  will  make  its  use 
clear.  Suppose  we  want  to  find  out  to  what  botanical 
species  the  morning-glory,  or  the  sweet  potato,  for  instance, 
belongs.  Turning  to  the  key  we  find  the  sub-kingdom 
of  Phaenerogams  —  flowering,  or  seed-bearing  plants  — 
divided  into  two  great  classes,  Angiosperms  and  Gymno- 
sperms,  as  already  explained  in  the  Sections  referred  to. 
A  glance  will  show  that  our  specimen  belongs  to  the 
former  class.  Angiosperms,  again,  are  divided  into  the 
two  subclasses  of  Dicotyledons  and  Monocotyledons 
(Sec.  129).  We  at  once  recognize  our  plant,  by  its  net- 
veined  leaves  and  pentamerous  flowers  as  a  dicotyledon 
(Sees.  37,  302),  and  turning  again  to  the  key,  we  find  this 


288  SYSTEMATIC   BOTANY 

subclass  divided  into  three  great  groups :  Sympetalous 
(called  also  Monopetalous  and  Gamopetalous) ;  Apopetal- 
ous  (or  Polypetalous);  and  Apetalous.  A  glance  will  refer 
our  blossom  to  the  sympetalous  or  monopetalous  group, 
which  we  find  divided  into  two  sections,  characterized  by 
the  superior  or  inferior  ovary  (Sees.  289,  294).  A  little 
examination  will  show  that  the  morning-glory  belongs  to 
the  former  class,  which  is  in  turn  divided  into  two  sections, 
according  as  the  corolla  is  regular,  or  more  or  less  irreg- 
ular. We  see  at  once  that  we  must  look  for  our  specimen 
in  the  former  class.  This  we  find  again  subdivided  into 
four  sections  according  to  the  number  and  position  of  the 
stamens,  and  we  find  that  the  morning-glory  falls  under 
the  last  of  these ;  "  Stamens  as  many  as  the  lobes  or  parts 
of  the  corolla  and  alternate  with  them."  A  very  little 
further  search  brings  us  to  the  family  Convolvulacea,  and 
turning  to  that  title  in  the  descriptive  analysis,  page  306, 
we  find  under  the  genus,  Ipomea,  a  full  description  of  the 
common  morning-glory,  in  the  species  Ipomea  pnrpurea, 
and  of  the  sweet  potato  in  the  species  Ipomea  batatas. 


APPENDIX 


BOOKS   FOR   READING  AND   REFERENCE 

An  excellent  bibliography,  accompanied  by  short  explanatory  notices 
of  the  works  most  useful  to  teachers  of  botany,  will  be  found  in  the 
seventh  chapter  of  Ganong's  Teaching  Botanist,  which  the  reader  is 
advised  to  consult.  Some  of  the  books  mentioned  there,  however,  are 
too  technical  to  fall  within  the  scope  of  this  work,  and  others  of  value 
have  appeared  since  the  list  was  compiled.  The  references  in  the 
following  pages  have  been  arranged,  as  far  as  possible,  with  regard 
to  the  subjects  treated  in  the  different  chapters  of  the  present  work ;  but 
the  order  of  treatment  by  different  authors  varies  so,  that  it  has  been 
impossible  to  specialize  closely.  Some  of  the  references  given  under 
one  head  will  be  found  to  contain  matter  equally  applicable  to  other 
subjects,  and  what  is  suitable  for  one  section  of  a  chapter  will  perhaps 
have  no  connection  with  the  other  parts  of  the  same  chapter.  The 
most  that  can  be  done  is  to  furnish  a  list  for  general  guidance,  as  an 
aid  to  those  teachers  who  have  not  access  to  well-stocked  libraries. 

The  price  of  all  the  works  named  has  been  given  wherever  it  could 
be  ascertained,  and  also  the  address  of  the  publishers  and  date  of  pub- 
lication. Where  more  than  one  reference  is  made  to  the  same  work, 
these  data  are  omitted  after  the  first.  With  one  or  two  exceptions,  no 
foreign  publications,  unless  reprinted  in  this  country,  are  included  in 
the  list.  Nearly  all  the  articles  quoted  from  the  Year  Books  of  the  De- 
partment of  Agriculture,  and  other  government  publications,  have  been 
reprinted  in  pamphlet  form,  and  can  be  obtained  free  by  addressing 
the  Bureau  of  Publication,  United  States  Department  of  Agriculture, 
Washington,  D.C.  A  circular  containing  a  list  of  all  the  publications 
of  the  department  will  be  sent  free  on  application. 

CHAPTER   II 

Allen  :  Story  of  the  Plants.  Chaps.  IV  and  V.  D.  Appleton  &  Com- 
pany, N.Y.  35  cents. 

Darwin:  Insectivorous  Plants.  D.  Appleton  &  Company.  1886. 
$2.00. 

Gray:  Structural  Botany,  pp.  85-131.  American  Book  Company, 
N.Y.  1880.  $2.00. 

ANDREWS'S  EOT.  —  19  289 


290 


APPENDIX 


Goodale:  Physiological  Botany,  pp.  337-353  and  409-424.  American 
Book  Company.  1885.  $2.00. 

Leavitt:  Outlines  of  Botany,  pp.  66-98.  American  Book  Company. 
1901.  $1.00. 

Lubbock :  Flowers,  Fruits,  and  Leaves ;  Last  Part.  Macmillan  Com- 
pany, N.Y.  1884.  $1.25. 

Ruskin :  Modern  Painters.  Vol.  V,  Chaps.  I,  II,  IV,  V,  IX,  X.  John 
Wiley  &  Sons,  N.Y. 

Dana:  Plants  and  Their  Children,  pp.  135-185.  American  Book 
Company.  1896.  65  cents.  (An  elementary  work,  but  full  of 
excellent  suggestions  and  examples.) 

Thoreau :  Autumn  Tints,  from  "Excursions  in  Field  and  Forest.'1 
Houghton,  Mifflin  &  Company,  Boston.  1891.  $2.00. 

Treat:  Home  Studies  in  Nature.  Part  III.  American  Book  Com- 
pany. 90  cents. 

Ward :  Disease  in  Plants.  Chaps.  Ill  and  IV.  Macmillan  Company. 
1901.  $1.60. 

Report  of  the  Division  of  Forestry:  United  States  Department  of 
Agriculture.  1899. 

CHAPTER  III 

Bailey :    The  Evolution  of  Our  Native  Fruits.     Macmillan  Company. 

1898.     $2.00. 

Gray:  Structural  Botany.     Chap.  VII. 
Leavitt:  Outlines  of  Botany,  pp.  147-156. 
Lubbock:  Flowers,  Fruits,  and  Leaves.     Part  II. 
Thoreau  :  "  The  Succession  of  Forest  Trees  "  and  "  Wild  Apples,"  from 

"Excursions  in  Field  and  Forest.1' 
Dana :  Plants  and  Their  Children,  pp.  27-49. 


CHAPTER   IV 

Dana:  Plants  and  Their  Children,  pp.  50-98. 

Goodale  :   Physiological  Botany,  pp.  205  and  384-396. 

Leavitt :  Outlines  of  Botany,  pp.  7-23. 

Lubbock:    Seeds  and   Seedlings.     D.  Appleton   &   Company.     1892. 

4  vols.     $10.00.  « 

Year  Book  of  the  United  States  Department  of  Agriculture.     1894. 

Pure  Seed  Investigation,  pp.  389-408 ;  Water  as  a  Factor  in  the 

Growth  of  Plants,  pp.   165-176. 
Year  Book.     1895.     Oil-producing  Seeds,  pp.  185-204;  Testing  Seeds 

at  Home,  pp.  175-184. 
Year  Book.     1896.     Migration  of  Weeds,  pp.  263-286  ;  Superior  Value 

of  Large,  Heavy  Seed,  pp.  305-322. 


APPENDIX 


29I 


Year  Book.     1897.     Additional  Notes  on  Seed  Testing,  pp.  441-452. 
Year  Book.     1898.     Improvement  of  Plants  by  Selection,  pp.  355-376. 
Grass  Seed  and  its  Impurities,  pp.  473-494. 

CHAPTER  V 

Gray :  Structural  Botany,  pp.  27-39  and  56-64. 
Leavitt :  Outlines  of  Botany,  pp.  34-45  ;  58-60. 
Ward  :  Disease  in  Plants.     Chaps.  V,  VI,  and  VII. 
Year  Book  of  the  United  States  Department  of  Agriculture.     1894 
Grasses  as  Sand  and  Soil  Binders,  pp.  421-436. 

CHAPTER  VI 

Apgar:  Trees  of  the  Northern  United  States.  Chaps.  II,  V,  and  VI. 
American  Book  Company.  1892.  55  cents. 

Leavitt:  Outlines  of  Botany,  pp.  45-56;  212-226;  229-240. 

Pinchot :  A  Primer  of  Forestry.  Bulletin  No.  24.  Division  of  Fores- 
try: United  States  Department  of  Agriculture.  1899. 

Popular  Science  Monthly,  September,  1901.  Plants  as  Water  Car- 
riers. 

Popular  Science  Monthly,  March,  1902.     The  Palm  Trees  of  Brazil. 

Ward:  The  Oak.     D.  Appleton  &  Company.     1892.     $1.00. 

Ward  :    Disease  in  Plants.     Chaps.  XXI,  XXII,  XXVI,  XXIX. 

Ward  :  Timber  and  Some  of  its  Diseases.  The  Macmillan  Company. 
1889.  $1.75. 

Year  Book.     1894.     Forestry  for  Farmers,  pp.  461-500.    (Bulletin  67.) 

Year  Book.  1895.  Principles  of  Pruning  and  Care  of  Wounds  in 
Woody  Plants,  pp.  257-268. 

Year  Book.     1898.     Pruning  of  Trees  and  Other  Plants,  pp.  151-166. 

CHAPTER   VII 

Gray:  Structural  Botany.     Chap.  V. 

Huntington :  Studies  of  Trees  in  Winter.     Knight  &  Millet,  Boston. 

1900.     $2.25. 

Leavitt:  Outlines  of  Botany,  pp.  23-33  and  138-143. 
Lubbock :  Buds  and  Stipules.     D.  Appleton  &  Company.     $1.25. 
Ruskin:  Modern  Painters.     Chaps.  Ill,  VI,  and  VII. 

CHAPTER   VIII 

Allen :  Flowers  and  Their  Pedigrees.    D.  Appleton  &  Company.    $i  .50. 
Dana:  Plants  and  Their  Children,  pp.  187-255. 

Darwin  :  Different  Forms  of  Flowers  of  the  same  Species.  D.  Appleton 
&  Company.  $1.50. 


292  APPENDIX 

Darwin :  On  the  Fertilization  of  Orchids.     $i  .75. 

Darwin:    Cross-  and    Self-fertilization    in    the    Vegetable   Kingdom. 

Chaps.  I  and  II.    $2.00.    Both  by  D.  Appleton  &  Company.    1886. 
Gray:  Structural  Botany,  pp.  163-214;  215-242. 
Henslow :  The  Origin  of  Floral  Structures  through  Insects  and  Other 

Agencies.     D.  Appleton  &  Company.     1895.     $1.75. 
Leavitt :  Outlines  of  Botany,  pp.  99-138- 
Lubbock :  Flowers,  Fruits,  and  Leaves  ;  First  Part. 
Lubbock:   British  Wild  Flowers  in  Relation  to  Insects.     Macmillan 

Company.     1893.     $1.25. 
Mueller:  The  Fertilization  of  Flowers.     Macmillan  Company.     1893. 

2is.  (about  $5.00). 
Trelease:  The  Yucca  Moth  and  Yucca  Pollination.     (Report  of  the 

Missouri  Botanical  Garden.)     1892. 
Ward :  Disease  in  Plants.     Chap.  VIII. 

Year  Book.     1896.     Seed  Production  and  Seed  Saving,  pp.  207-216. 
Year  Book.     1897.     Hybrids  and  Their  Utilization  in  Plant  Breeding, 

pp.  383-420. 

Year  Book.     1898.     Pollination  of  Pomaceous  Fruits,  pp.  167-180. 
Year  Book.     1899.     Progress  of  Plant  Breeding  in  the  United  States, 

pp.  465-490- 
Year  Book.     1900.     Smyrna  Fig  Culture  in  the  United  States,  pp.  79- 

106. 

CHAPTER   IX 

Allen :  Colin  Clout's  Calendar.    Particularly  Chaps.  XXXVI-XXXVIII. 

Funk  &  Wagnalls  Company,  N.Y.     1883.     Cloth,  $1.00 ;  paper,  25 

cents. 

Bailey:   The  Survival  of  the  Unlike.   Macmillan  Company.    1897.   $2.00. 
Darwin :  The  Variation  of  Animals  and  Plants  under  Domestication. 

Chaps.  IX-XII.     D.  Appleton  &  Company.     2  vols.     $5.00. 
Dawson :  The  Geological  History  of  Plants.     D.  Appleton  &  Company. 

$i-75- 

Ward :  Disease  in  Plants.     Chaps.  VII,  X,  XI,  XVII,  and  XIX. 
Contributions  from  the  United  States  National  Herbarium  :  — 

The  Plant  Covering  of  Ocracoke  Island.   Thomas  Kearney.  Vol. 

V,  No.  5.     1900. 

Plant  Life  of  Alabama.     Chas.  Mohr.     Vol.  VI.     1901. 
Year  Book.      1894.      The  Geographic  Distribution   of  Animals  and 

Plants  in  North  America,  pp.  203-214. 

Year  Book.     1895.     The  Grasses  of  Salt  Marshes,  pp.  325-332. 
Year  Book.     1898.     Weeds  in  Cities  and  Towns,  pp.  193-200.     Forage 

Plants  on  Alkali  Soils,  pp.  535-550. 

The  Water  Hyacinth  in  its  Relation  to  Navigation  in  Florida.     Bulletin 
18.     United  States  Department  of  Agriculture. 


APPENDIX  293 


CHAPTER  X 

Clute :    Our  Ferns  in  Their  Native  Haunts.      Frederick  A.  Stokes  & 

Company,  N.Y.     igoi.     $2.15. 
Huxley  and  Martin  :   "  Algae  "  and  "  A  Study  of  Pteris  Aquilina,"  from 

"  A  Course  of  Elementary  Instruction  in  Practical  Biology."     Mac- 

millan  Company.     1886.     $2.60. 
Leavitt:  Outlines  of  Botany,  pp.  163-183,  198-212. 
Parsons  (Mrs.  Dana)  :    How  to  know  the  Ferns.      Charles  Scribner's 

Sons,  N.Y.     1899.     $1.50. 
Underwood  :    Our  Native  Ferns  and  Their  Allies.     6th  revised  edition. 

Henry  Holt  &  Company,  N.Y.     1900.     $1.00. 


CHAPTER  XI 

Atkinson :    Mushrooms :    Edible  and  Poisonous.      Andrus  &  Church, 

Ithaca,  N.Y.     1900.     $3.00. 
Gibson :  Our  Edible  Toadstools  and  Mushrooms.     Harper  &  Brothers, 

N.Y.     $7.50. 

Leavitt:  Outlines  of  Botany,  pp.  183-197.  . 

Marshall :    The  Mushroom  Book.     Doubleday,  Page  &  Company,  N.Y. 

1901.     $3.00. 
Massee:  Text  Book  of  Plant   Diseases.     Macmillan  Company,  N.Y. 

1899.     $1.60. 
Mcllvaine :  One  Thousand  American  Fungi.     2d  edition.     The  Bowen 

Merrill  Company,  Indianapolis.     1902.     $5.00. 

Ward :  Timber  and  Some  of  its  Diseases.     Chaps.  V,  VI,  VII,  X-XIII. 
Year  Book.     1894.     Grain  Smuts:    Their  Cause   and  Prevention,  pp. 

409-420. 
Report   of  the   Department   of  Agriculture.      1885.      Twelve   Edible 

Mushrooms  of  the  United  States.     (Reprinted  as  a  Bulletin,  1890.) 
Report   of  the   Secretary  of  Agriculture.     1890.     Mushrooms   of  the 

United  States,  pp.  366-373. 

Year  Book.  1897.  Some  Edible  and  Poisonous  Fungi,  pp.  453-470. 
Year  Book.  1900.  Fungous  Diseases  of  Forest  Trees,  pp.  199-210. 
Cereal  Rusts  of  the  United  States.  Bulletin  No.  16.  United  States 

Department  of  Agriculture. 
How  to  grow  Mushrooms.     Bulletin  53. 
Mushroom  Poisoning.     Circular  No.  13.     Department  of  Agriculture. 


294 


APPENDIX 


BOOKS   FOR   GENERAL   REFERENCE 


1.  Allen:  The  Story  of  the  Plants.     D.  Appleton  &  Company,  N.Y. 

35  cents. 

2.  Bailey :  New  Encyclopedia  of  American  Horticulture.     The  Mac- 
millan  Company,  N.Y.     1900.    4  vols.     $20.00.     (By  subscription 
only.) 

3.  Bailey :    Talks  Afield.      Houghton,    Mifflin  &  Company,  Boston. 

1896.     $1.00. 

4.  Boyle:    The  Woodland's  Orchids.     Macmillan  Company.     1901. 

5.  Campbell:  The  Evolution  of  Plants.     Macmillan  Company.     1899. 
$1.00. 

6.  Crozier :  A  Dictionary  of  Botanical  Terms.      Henry  Holt  &  Com- 

pany, N.Y.     1892. 

7.  Darwin  :    The  Power  of  Movement  in  Plants.    D.  Appleton  &  Com- 
pany.    1886.    $2.00. 

8.  De  Candolle:   The  Origin  of  Cultivated  Plants.     D.  Appleton  & 
Company.     1884.     $2.00. 

9.  Ganong:   The  Teaching  Botanist.      Macmillan  Company.     1899. 

$1.10. 
10.  Geddes :    Chapters  in  Modern  Botany.      Charles    Scribner's  Sons, 

N.Y.     1893.     $1.25. 
n.  Gray:    Structural  Botany.     American  Book  Company,  N.Y.    1880. 

$2.00. 

12.  Jackson:  A  Glossary  of  Botanic  Terms.     J.  B.  Lippincott   Com- 
pany, Philadelphia.     1900.     $2.00. 

13.  Kerner  &  Oliver:  Natural  History  of  Plants.     Henry  Holt  &  Com- 
pany, N.Y.     1896.     $15.00. 

14.  Sorauer:     A    Popular    Treatise    on    the    Physiology    of    Plants. 
Longmans,  Green   &   Company,   London   and  N.Y.     1895.      9*. 
(about  $2.50). 

15.  Vines:    Lectures  on  the  Physiology  of  Plants.     Macmillian  Com- 

pany.    1895.     $5.00. 

Of  the  works  named  above,  Nos.  2  and  13  are  expensive  and  not 
likely  to  be  accessible  except  in  communities  where  there  is  a  well- 
stocked  public  library.  Kernels  work  is  written  in  a  simple,  popular 
style,  and  so  profusely  and  beautifully  illustrated  as  almost  to  explain 
itself  without  the  text.  No.  2,  as  its  name  implies,  treats  more  partic- 
ularly of  botany  in  its  practical  relations  to  horticulture.  No.  14  is  a 
simple,  practical  treatise,  easily  understood,  and  as  free  from  techni- 
calities as  the  nature  of  the  subject  will  permit. 

No.  ii  can  be  consulted  with  advantage.  It  is  written  in  such  a 
clear,  intelligible  style,  and  makes  so  plain  the  subjects  with  which  it 
deals,  that  the  student  will  find  it  very  helpful. 


APPENDIX  295 


HANDBOOKS 

1.  Britton:  A  Manual  of  the  Flora  of  the  Northern  States  and  Canada. 
Henry  Holt  &  Company,  N.Y.     1898.     $2.25. 

2.  Britton  &  Brown  :  An  Illustrated  Flora  of  the  Northern  States  and 
Canada.     Charles  Scribner's  Sons,  N.Y.     1898.     3  vols.     $9.00. 

3.  Chapman  (A.  W.)  :    Flora  of  the  Southern  States.     Revised  ed. 
1897.     $4.00. 

4.  Coulter :  A  Manual  of  the  Botany  of  the  Rocky  Mountain  Region. 
1885.     $1.62. 

5.  Gray :  Manual  of  the  Botany  of  the  Northern  United  States.     6th 
ed.     Revised.     1890.     $1.62. 

6.  Gray:    Field,  Forest,  and  Garden  Botany.     New  ed.,  revised  by 
Bailey.     1895.     $1.44. 

7.  Willis:    Practical   Flora.      1894.      $1.50.      3-7  by  the   American 
Book  Company. 

8.  Watson  £  Brewer :  Botany  of  California.     From  the  United  States 
Geological  Survey.     2  vols.     1875-1880.     Has  been  republished  by 
the  State  government  of  California,  and  will  be  found  useful  to 
students  on  the  Pacific  slope. 

Teachers  desiring  to  do  only  elementary  work  will  find  the  Flora  in 
Gray's  little  book,  "  How  Plants  Grow,''  a  very  convenient  handbook. 
80  cents. 

For  persons  not  sufficiently  versed  in  Systematic  Botany  to  use  the 
manuals,  a  number  of  attractive  guides  have  been  prepared,  some  of 
which  are  named  below  :  — 

9.  Apgar :    Trees  of  the  Northern   United   States.     American  Book 
Company.     $1.00. 

10.  Creevey:  Flowers  of  Field,  Hill,  and  Swamp.     Harper  &  Brothers. 
1897.     $1.75. 

11.  Keeler:    Our   Native   Forest   Trees.      Charles    Scribner's    Sons. 
1900.     $2.00. 

12.  Lounsberry  (Alice):    Southern  Wild  Flowers  and  Trees      Fred- 
erick A.  Stokes  &  Company.     1901.     $3.75. 

13.  Matthews  :  Familiar  Trees  and  Their  Leaves.     1896.     $1.75. 

14.  Matthews:  Familiar  Flowers  of  Field  and  Garden.     $1.40.     Both 
by  D.  Appleton  &  Company. 

15.  Field  Book  of  American  Wild  Flowers.     G.   P.   Putnam's  Sons. 
1902.     $1.75. 

16.  Newhall :  The  Trees  of  Northeastern  America.     1891. 

17.  Newhall:  The  Shrubs  of  Northeastern  America.     1893. 

18.  Newhall :  The  Vines  of  Northeastern  America.    1897.    $1.75  each. 
16-18  bv  G.  P.  Putnam's  Sons,  N.Y. 


296  APPENDIX 

19.  Parsons  (Mrs.  Dana)  :  How  to  know  the  Wild  Flowers.     Charles 
Scribner's  Sons.     1897.     $2.00. 

20.  Wright :  Flowers  and  Ferns  in  Their  Native  Haunts.     Macmillan 
Company.     1901.     $2.00. 


PERIODICALS 

The  science  of  Botany  is  advancing  so  rapidly  that  a  book  is  very 
soon  out  of  date,  and  one  who  wishes  to  keep  abreast  of  the  current  of 
progress  should  have  access  to  one  or  more  of  the  standard  periodical 
publications  dealing  with  the  subject.  Some  of  the  most  available  for 
general  use  are :  — 

The  Botanical  Gazette,  University  of  Chicago.     Monthly.     $4.00. 

Bulletin  of  the  Torrey  Botanical  Club,  Lancaster,  Pa.     $2.00. 

Forest  Leaves.  Pennsylvania  Forestry  Association,  Philadelphia.  Bi- 
monthly. $1.00. 

The  Plant  World.  Binghamton,  N.Y.,  and  Washington.  D.C.  Bi- 
monthly. $1.00. 

Science.  Lancaster,  Pa.,  and  Macmillan  Company,  N.Y.  Weekly. 
$5.00. 

Rhodora.  Published  by  the  New  England  Botanical  Club,  Boston, 
Mass.  Monthly.  $1.00. 


INDEX 


In  the  Index  the  numbers  in  Roman  type  (295)  refer  to  sections :  those  in  full- 
face  type  (39)  refer  to  cuts. 


Aborted 295-313 

Accessory  buds 263 

Accessory  fruits in 

Achene ...  88 


Acuminate  leaf. 

Acute  leaf 40 

Adhesion 303 

Adjustment  of  leaves 54-65 

Adnate 32,  284,  393 

Adventitious  buds 178,  263 

Adventitious  roots 187 

.Ecidiomycetes 403 

^Ecidium 403 

Aerial  roots 186 

Aerial  stems 201 

Estivation 290 

Aggregate  fruits 112 

Albuminous 125 

Algae 357.  377-383 

Alternate  leaves 50 

Alternation  of  generations, 

364,  368, 370,  375 

Ament 272 

Amentaceous 311 

Amphitropous 226 

Anatomy  of  plants 3 

Anatropous 131,  227 

Anemophilous 332 

Angiosperms 128 

Annuals 180 

Annuius 391 

Anther 284 

Antheridia 366 

Apetalous 304 

Apex 36,  130 

Apopetalous 304,  305 

Appendage 316,  317,  318 

Arch  of  the  hypocotyl 153 

Archegonia 366 

Aril 317 

Ascending 202 

Asexual  generation 368 


Ash 196,  197,  200 

Assurgent 202 

Asymmetrical 291 

Auricled 37 

Axial  placenta 109 

Axial  root '. 172 

Axil 32,50 

Axillary  buds 241 

Axis 178,  246,  265,  266,  267 

Bacteria 198,  385 

Bacteriology i 

Base 36, 130 

Basidia 394 

Bast 219,  224 

Berry 79 

Biennial 180 


Bilabiate 308 

Black  rust 400 

Blade  of  leaf 31 

Bract 103 

Bryophytes 358 

Bud 241,  249-263 

Bud  scales 243 

Bulb 193 

Button  (of  mushroom) 389 

Calyx 74,  282,  309 

Cambium 220,  224 

Campanulate 422 

Campylotropous 131,  225 

Capitate 295 

Capsule 93 

Carbohydrates 26 

Carbon  dioxide 18,  24 

Carpels 74,  103 

Carpophore 89 

Caruncle 123 

Caryopsis 91 

Catkin 272 

Cedar  apples 406 

Cell 9.78,287 


297 


INDEX 


9  213 

Determinate  inflorescence. 

265 

Diadelphous  

299 

58 

Diatoms  
Dichotomous  

382 
246 
.  .  .  .121-129 

Centrifugal  inflorescence.. 
Centripetal  drainage  
Centripetal  inflorescence  .  . 
Chalaza  121, 
Chlorophyll  
Circinnate  

277 

58 
268  ' 

122,  123,  130 
25 
26l 

108 

Dimorphic  

331 
331 
311 

Dimorphous  

Uircumsc 

34 
3*4 

Dispersal  of  seed  
Distinct  

....133-136 

3°3 
262 

Cleistogamic  flowers  

Clipped  seed.  .  .  (See  page  90,  Material) 

96 

58 

Cohesion  

3°3 

278 

Drupe  

80 

Collective  fruits  

"3 
338 
.    .  61 

Ecoloev 

5.339 
341 
327 

C°      ass     lants 

Ecological  factors  
Eog  cell  

C        1       fl 

Compound  leaf  

45-  49 
..........260 
38i 

Emarginate  
Embryo  
Embryology  

43,44 

118 
329 

Conjugation  

Connate  
Convolute  
Cordate 

34 
256,  290,  293 
34 

227 

118,  123,  125 
06 

06 

219 

Epidermis  174, 

176,  191,  219 
294 

Corolla  

268 

Essential  constituents  

197 

283 

Il8,  121,  122 
89 

50 

Cremocarp  
Crenate 

Ex-albuminous  

125 
391 

<u6 

Exosmose  

227 

.   284 

Fall  of  the  leaf 

64 

Culm 

46 

Cycle  of  growth  
Cyme  

jrg 

Fascicle  
Fascicled  roots  

276 

171 
38 

Declined  

202 

Fertilization  

324.327. 

Definite  annual  growth.  .  . 

Fibrovascular  bundle.  .  .43,  215,  217,  224 
Filament,  a  hairlike  appendage  293 

Definite  inflorescence  
Dehiscent  fruits  
Deliquescent  
Deltoid  

265 

8^ 

240 

32 

Filamentous  algae  
Fission  
Floral  envelopes  
Follicle 

377.379 
080 

49 

282 
94 
•289,303,393 
.  .  .  100 

Descriptive  .botanv  

.6 

o«2 

Free 

Determinate  erowth.  .  . 

Free  central  nlacenta.  .  . 

INDEX 


Free  veining 361 

Function 8 

357.384 

75 


Funiculus . 


Gametes  . . . 


367 


Gametophyte  ......................  367 

Gamopetalous  .....................  292 

Gamosepalous  .....................  292 


Gemmas 


070 


Genus  ............................  4II 

Geophilous  ........................  352 

Geotropism  ..........    ............  160 

Germ  .............................  n8 


327 
137-144 


Germ  cell 

Germination 

Gills  (of  mushroom) ~.  .393 

Glabrous 

Glaucous 

Grain 91 

Grain  of  timber 238 

Gravity 16] 


Inflexed 26 

Inflorescence. 26 

Insectivorous  plants 70,  7 

Internode 5 

Introrse 28 

Inverted  seed I3 

Involucre  . . . 


Involute 261,  39 

Irregular  flower 


Keel. . 
Knots. 


Growth 


155 


Gymnosperms 120,  127 

Gymnosporangium 406 

Halophyte 348 

Hastate 38 

Haulm 207 

Haustoria 184 

Head 273 

Heartwood. 236 

Herbaceous 201 

Heliotropism 57 

Hilum 121,  130,  131 

H  istology 3 

Horizontal  seed 132 

Host  plant 184 

Hydrophytes 348,  349 

Hymenium 394 

Hymenomycetes 394 

Hyphae 388 

Hypocotyl 118,  121 

Hypogynous 289 

Imbricated 250 

Imperfect  flower 291 

Incomplete  flower 291 

Indefinite  annual  growth 247 

Indefinite  inflorescence 265 

Indefinite  number  of  parts 296 

Indehiscent  fruit 84 

Indeterminate  growth 247 

Indeterminate  inflorescence  . . .  .265,  266 
Indusium 362 


70,39: 
Lanceolate  .........................  g' 

Lateral  buds  ......................  24 

Leaf  attachment  ....................  3, 

Leaf  cups  ..........................  $< 

Leaf  scars  ........................  24; 

Leaf  traces  ........................  2i< 

Legume  ....  .......................  Q< 

Lenticels  .......................  17,  2i< 

Ligulate  ...........................  30; 

Life  cycle  .........................  40= 

Lobing  .............................  ^ 

Loculicidal  ........................  IQI 

Loculus  ...................  78,  105,  28; 

Loment  ...........................  IQC 

Lyrate  .............................  33 


Medulla  ...........................  215 

Medullary  rays  ................  174,  222 

Megasporangia  ....................  370 

Megaspore  ........................  370 

Megasporophyll  ...................  370 

Meri  carps  ..........................  89 

Metabolism  ........................  30 

Mesophyte  ....................  348,  353 

Midrib  ...........................  a8 


Microsporangia 370 

Microspore 370 

Microsporophyll 370 

Micropyle 120,  121.  130 

Monadelphous 299 

Monocarpellary 93 

Monocotyledons 119 

Monoecious 311 

Monopetalous 292 

Monosepalous 292 

Morphology 2 

Mosaic  (leaf) , 


•55 

Mucronate 47 

Multiple  fruit 113 

Mushroom 397 

Mycelium 388 

Mycetes 388 


Inferior  ovary .289  j  Mycology I 


300 


INDEX 


Net-veined 37 

Neutral  flower 3IQ 

Node 5° 

Nucleus 9 

Numerical  plan 288 

Nut 87 

Obcordate 45 

Oblique 36 

Obovate 30 

Obsolete 295 

Obtuse 41 

Oospore 367 

Opposite  leaves 50 

Organ 8 

Organs  of  reproduction 151 

Organs  of  vegetation 151 

Orthotropous 130 

Osmose 227 

Oval 29 

Ovary 73,  285,  287 

Ovule 287 

Paleobotany I 

Palmate  veining 38 

Panicle 270 

Papilionaceous 298 

Pappus 88 

Parallel  veining 37 

Paraphyses 394 

Parasitic  plants 184 

Parenchyma 213 

Parietal 103 

Pedicel 264 

Peduncle 75,  103,  264 

Peltate 34 

Pentamerous 296,  302 

Pepo 78 

Perennial 181 

Perfect  flower 291 

Perfoliolate 24 

Perianth 282 

Pericarp 74 

Perigynous 297 

Persistent 32 

Personate 308 

Petals 282 

Petiole 31,33 

Phanerogams 355 

Photosynthesis 24 

Phyllotaxy 50-53 

Pileus 


392 

Pinna 360 

Pinnate  veining 38 

Pinnule . . . .- 360 

Pistil 283,  285 

Pistillate 3IO 

Pitcher  plant 7o 


Pith 191.  219 

Placenta 75,  103,  287 

Plicate 124,  254 

Plumule 118, 121 

Pollen 284 

Pollen  grains 284 

Pollen  sac 284 

Pollen  tubes 325 

Pollination 286 

Polycotyledons 120 

Polymorphic 407 

Polymorphism 386,  407,  408 

Polypetalous 304 

Pome 74 

Prefloration 290 

Prefoliation 254 

Primary  root 170 

Pronuba 334 

Protection 72,  335 

Prothallium 366 

Protoplasm 9,  213 

Pteridophytes 359 

Pubescent 36 

Puccinia 400 

Raceme 267 

Rachis 45,  264 

Radial  roots 172 

Radial  section 237 

Raphe 122,  131 

Ray  flowers 307 

Receptacle 74,  75,  103,  282 

Red  rust 399 

Region  of  growth 148,  153,  157 

Regular  flower 291 

Respiration 28 

Revolute 261,  392 

Rhizoids 372 

Rhizoma 189 

Ribs 39 

Ringent 308 

Rings  of  growth 221,  223,  224 

Root  cap 


150 

Root  growth 148,  150,  153,  172 

Root  hairs 149 

Root  pressure 229 

Root  pull 165 

Rootstock 188 

Rosette 55 

Rostelia 406 

Rotate 420 

Rudimentary  organs 313 

Rugose 36 

Runcinate 53 

Runner  ...  . . .208 


Sagittate 35 

Salver-shaped 421 


INDEX 


301 


Samara 90 

Sap  movement  226,  227,  231,  232,  233,234 

Saprophyte 185 

Sapwood 236 

Scale  leaves i    . .  .68 

Scape 193 

Scion 208 

Scorpioid  inflorescence 278 

Secondary  roots 170 

Seed  vessel 73 

Sepals 74,  282 

Septa 106 

Septicidal 106 

Septifragal 107 

Serrate 48 

Sessile 34, 

Sexual  generation 368 

Silicic 102 

Silique 101 

Sinuate 52 

Sleep  movements 62,  63 

Sori 362,399 

Spathe 292 

Spatulate 28 

Species 411 

Spermatophytes 126,  355 

Spike 271 

Spine 32,  68,  209,  210 

Spirogyra 379 

Sporangia 363 

Spore 363.364.396 

Spore  print 395 

Sporidia 402 

Sporophyll 370,  375 

Sporophyte 365 

Stamen 283,  284 

Staminate  flower 310 

Staminodia 315 

Starch 26,  118,  119,  192,  200 

Stems 201-212 

Sterile  flower 310 

Stigma .285 

Stigmatic  surface 293 

Stipe 360 

Stipe  of  mushroom 391 

Stipel 300 

Stipule 31,  32 

Stolon 208 

Stomata 16 

Stone  fruit 80 

Storage  of  food 125,  192,  196 

Style 285 

Suckers 208 

Summer  spores 401 

Sundew 71 

Superior 289 

Supernumerary  buds 263 

Suppressed 295,  313 


Suspended  seed 132 

Suture 94.  98,  103 

Symbiosis 340 

Symmetrical  flower 291 

Symmetry 36,  291 

Sympetalous 292,  304,  306 

Syncarpous 103 

Syngenesious 428 

Synsepalous 292 

Systematic  botany 6 


Tangential  section 

Tap  root 

Taxonomy 

Tegmen 

Teleutospore 

Tendril 32,  67, 

Terete . . . 


Terminal  bud 

Testa 

Tetradynamous 

Tetramerous 

Thallophytes 

Thallus 357, 

Tissue 

Toadstools 

Torus  . . . 


237 

170 

6 

.  122,  123 

401 

203,  211 

207 

241 

.122,    123 

295 

295.   3°2 

357 

366,  371 


Trama 

Transformation  of  leaves 

Transformation  of  organs.  .31^ 

Transpiration 

Trifoliolate 

Trimerous 

Trimorphic 

Truncate 

Tuber 

Tunicated 

Twining  stems 

Twining,  cause  of 


397 

.  .75,  282 

394 

...66-72 
320,  321 

IS 

46 

.  288,  302 

331 

36 

190 

194 

203 

.  162,  204 


Umbel 

Undulate 

Unisexual 

Unsymmetrical 

Urceolate 

Uredo 

Uredospore 


...........  269 

51 


...........  291 

..........  423 

...........  399 

...........  399 


Valvate 257 

Valves 99 

Vascular  bundles 43,  214,  217,  224 

Vascular  cylinder 174 

Vascular  cryptogams 359 

Vascular  system 214 

Vascular  tissue 10,  191 

Vegetable  physiology 4 

Vegetative  multiplication 380 

Veil 39° 


302 


INDEX 


Veins  
Ventral  

37-43 
96 

Water  roots  
Whorled  leaves  

183 
5i 

Versatile 

284 

Wings 

Verticel 

Vexillum  

298 

Viscid  

36 

048 

Vitality  of  seeds  

I42 

Vittae 

89 

Volva 

Water  holders... 

..."» 

Yucca  moth.  .  . 

.  .  .^^4 

Aids  to  Field  and  Laboratory  Work 
in   Botany 

Apgars'  Plant  Analysis.     By  E.  A.  and  A.  C.  APGAR. 

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A  book  of  blank  schedules,  adapted  to  Gray's  Botanies,  for  pupils' 
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Apgar's  Trees  of  the   Northern    United   States 

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